Ira M. Bernstein
Cathleen Harris
Immediate Concerns
The evaluation of pregnant patients with surgical disorders and trauma is complex, owing to the fact that the woman and her fetus are both regarded as patients. The well-being of the fetus depends entirely on the stability of the physiologic processes of the pregnant woman. Knowledge of normal physiologic changes of pregnancy is essential, as increased morbidity and mortality for mother or baby can result from delays in diagnosis and treatment. This chapter will summarize the approach to the gravid patient with surgical disease, including clinical assessment, diagnostic studies, interpretation of laboratory values, and specific considerations for various clinical conditions.
Approximately 1 in 500 (0.2%) of pregnant women require surgery for nonobstetric conditions (1). Appendectomy, cholecystectomy, and adnexal procedures constitute the most common surgeries during pregnancy. Although pregnancy outcomes after surgery are often good, fetal loss rates can be as high as 2% to 20%, depending on the condition (1). This fact highlights the importance of thoughtful management in these cases. Trauma is an additional important cause for surgical intervention during pregnancy. Most series report the incidence of trauma to be approximately 8%, or 1 in 12 pregnancies (2). Trauma is the leading cause of nonobstetric maternal death, and fetal losses can be significant. One should always consider the possibility of pregnancy in any female between 12 and 44 years of age presenting with abdominal pain or trauma.
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Table 100.1 Key points in the ABCs of the resuscitation of pregnant women |
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As in nonpregnant individuals, the first task is to ensure that airway, breathing, and circulation (ABCs) are adequate. It is important to give first priority to these basic elements, because adequate maternal oxygenation and uteroplacental perfusion are the means by which the fetus is also resuscitated. Attention should always be paid to achieving hemodynamic stability in the mother first, before evaluation and treatment of pregnancy issues. Physiologic adaptations of pregnancy affect the clinician's ability to address the ABCs, and key points that should be considered in the pregnant trama victim are summarized in Table 100.1.
Once assured that the patient is hemodynamically stable, attention is turned to a more detailed secondary assessment. This is centered on evaluation of specific injuries or organ systems, as well as the pregnancy itself. A focused patient history is central to the evaluation of abdominal pain or trauma during pregnancy. Abdominal symptoms can be nonspecific during pregnancy, so it is especially valuable to clarify the location, intensity, and quality of pain, including associated symptoms and aggravating or alleviating factors. Any obstetric symptoms, such as contractions, cramps, bleeding, or fluid leakage, should be noted. In the case of trauma, important details of the incident should be elicited, including vehicle speed, position seated in the vehicle, use of restraints, airbag deployment, and injuries to the head, abdomen, or extremities.
Understanding normal physical changes and common complaints associated with pregnancy will help the clinician to determine which symptoms are benign and pregnancy-related versus pathologic. Many patients report nausea and vomiting in early pregnancy, but these symptoms are not typical in the latter two trimesters. Pyrosis due to acid reflux is reported by many gravidas, but is often easily relieved with antacids. Constipation is a common complaint, due to the increased transit time of the gastrointestinal tract. Transient discomfort or intermittent contractions are not rare, but persistent, rhythmic, or severe abdominal pain merits evaluation. In all trimesters, right lower quadrant pain may signal appendicitis. Colicky right upper quadrant pain is suggestive of cholelithiasis, and the symptom profile for biliary tract disease in pregnant women is similar to that of their nonpregnant counterparts.
In the third trimester, it is important to evaluate and exclude the possibility of obstetric complications such as preterm labor (PTL), premature rupture of membranes, placental abruption, and intrauterine infection. A basic obstetric (OB) triage evaluation includes external fetal heart rate monitoring, assessment of contractions, palpation of the uterine fundus, speculum examination for pooling, Nitrazine and fern tests, and digital cervical examination.
A suggested approach to the initial evaluation of the pregnant patient with surgical diseases or trauma is shown in Table 100.2.
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Table 100.2 Key steps in the approach to the pregnant patient with surgical diseases or trauma |
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Diagnostic Studies
Laboratory Values
When common laboratory tests are evaluated during pregnancy, results can be misinterpreted or confusing unless pregnancy-specific norms are considered. Physiologic changes of pregnancy, including increased blood and plasma volumes, hormone production, and altered metabolic clearance, cause changes in the plasma concentration of many analytes. Selected laboratory values of interest are displayed in Table 100.3 (3).
OB Tests of Interest
Fetal Fibronectin
Fetal fibronectin (fFN) is a protein produced by fetal membranes involved in adhesion of the placenta and membranes to maternal tissues. Between 24 and 34 weeks, fFN is not normally detectable in cervicovaginal secretions. The presence of fFN may indicate a disruption of the membranes and decidua, due to inflammation or other causes. Numerous studies have shown success in using fFN to predict preterm birth. The clinical utility of the test rests in its high negative predictive value. In a symptomatic patient, a negative test is associated with greater than 95% likelihood of not delivering within 14 days. This information is useful in the management of patients with preterm contractions, not uncommon in the setting of surgical diseases complicating pregnancy (4).
Amniocentesis
In selected cases, evaluation of amniotic fluid may be important to exclude intrauterine infection as a cause of abdominal pain. Abnormal findings in amniotic fluid suggestive of bacterial infection include bacteria seen on Gram stain and/or positive culture. Low glucose, typically less than 15 mg/dL, and a high white cell count are also highly suspicious. In addition, inflammatory markers such as high granulocyte colony-stimulating factor (G-CSF), tumor necrosis factor (TNF)-α, interleukin (IL)-1, and IL-6 are strongly suggestive of amnionitis. Because there is a risk of preterm contractions, premature rupture of the membranes, or fetal loss due to the procedure, amniocentesis should be done on a selective basis. However, these data can be extremely useful when the clinical picture is unclear (5).
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Table 100.3 Normal laboratory values during pregnancy |
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Diagnostic Imaging Studies
Several modalities are available for diagnostic imaging to aid in the evaluation of surgical diseases of pregnancy. Medically necessary diagnostic tests should not be withheld solely on the basis of pregnancy, but one should contemplate the potential advantages and disadvantages when selecting a particular testing method.
Ultrasonography uses sound waves and thus does not expose the patient to ionizing radiation. There are no known adverse fetal outcomes associated with the use of prenatal diagnostic ultrasound under current clinical guidelines for energy exposure. Magnetic resonance imaging (MRI) makes use of the altered energy state of protons to enhance imaging. Its chief clinical uses have been to evaluate placental abnormalities and characterize fetal central nervous system (CNS) malformations; however, increasing experience in the acute setting suggests MRI may also be a valuable tool for assessing for intra-abdominal pathology. To date, MRI has been used safely during pregnancy and is consistent with American College of Radiology guidelines, as discussed below. X-ray studies and computed tomography (CT) involve ionizing radiation, and for this reason need to be used judiciously in gravid patients (6).
Obstetric Ultrasound
Obstetric ultrasound serves to confirm fetal viability and offers the opportunity to assess fetal size, anatomy, amniotic fluid volume, and placental location (6). This information provides the basis for decision making in pregnant patients. A basic study can be completed quickly at the bedside and can be done at the time of sonographic evaluation for other indications, such as right upper quadrant ultrasound.
Sonography for Trauma
In the setting of trauma, surgeon-performed focused assessment with sonography for trauma (FAST [focused assessment with sonography for trauma]-US [ultrasound]) is a useful screening tool. At one institution, FAST-US was used not only for trauma evaluation, but as a screen for pregnancy, and 18 of 144 (11%) of patients were newly diagnosed with pregnancy using this procedure. Because of this, FAST-US contributed to a significant decrease in radiation exposure when compared to other trauma patients diagnosed with pregnancy based on serum human chorionic gonadotropin (HCG) screening (7).
FAST-US done to detect intra-abdominal bleeding after trauma has a similar sensitivity and specificity among pregnant and nonpregnant patients. In one study of 127 pregnant trauma patients, ultrasound examination identified intraperitoneal fluid in 5 of 6 patients and was negative in 117 of 120 patients without intra-abdominal injury. Patients with false-positive scans had serous fluid (8). In reproductive-age women with blunt abdominal trauma, free fluid in the cul de sac has been associated with a higher injury rate compared to no free fluid in both pregnant and nonpregnant women. Thus, free fluid is not necessarily a normal or physiologic finding (9).
Ultrasonography is of limited value in the diagnosis of placental abruption after trauma. In fact, ultrasound may miss up to 50% to 58% of cases. The echotexture may be very similar to that of placental tissue, so identification of retroplacental bleeding is not always possible (10,11).
Appendicitis
Graded compression ultrasonography is the initial test of choice in the assessment of appendicitis during pregnancy. Imaging is focused on the self-reported area of maximal pain. The overall accuracy of this technique in diagnosing appendicitis is 86%. However, accuracy may be limited in the setting of a retrocecal appendix or perforated appendicitis, both of which are more common in the gravid patient. Color Doppler sonography can be used as an adjunct for improving the sensitivity of the test. In a series of 42 women with suspected appendicitis during pregnancy, ultrasound was found to be 100% sensitive, 96% specific, and 98% accurate in diagnosing appendicitis (12).
Biliary Tract Disease
The diagnosis of cholelithiasis during pregnancy is similar to that in the nonpregnant patient. Visualization of stones in the gallbladder is reported to be as high as 95% using sonography. Although detection of gallstones in a patient with right upper quadrant pain is suggestive of acute cholelithiasis, other features should be considered, such as gallbladder wall edema or thickening >4 to 5 mm. The Murphy sign can also be elicited, as the patient experiences pain from pressing the transducer over the gallbladder (13).
Computed Tomography
Computed tomography (CT) may be considered for evaluation of the abdomen if the initial examination or other studies are equivocal. The most common indication for CT is blunt abdominal trauma after motor vehicle crashes (13). Other common indications include appendicitis and renal colic. One study of helical CT revealed good success in detecting injuries after trauma during pregnancy. In this cohort, 17 women (35%) had normal evaluations, 11 patients (23%) had abnormal placental enhancement, and 1 uterine rupture occurred. Fifteen women (31%) had nonuterine injuries, and 27% had both uterine and other maternal injuries. The estimated radiation exposure due to helical CT was estimated to be 8.7 to 17.5 mGy, depending on technique (14). Although there are limited data regarding the accuracy of CT for the diagnosis of appendicitis during pregnancy, one series of seven patients correctly identified all cases (15). Depending on the protocol, pelvic CT can deliver a dose of radiation to the fetus as high as 2 to 5 rad. Although the threshold for teratogenesis may not be reached with this level of radiation exposure, the relative risk of childhood cancer may be increased. The odds of dying of childhood cancer increase from a baseline of 1 in 2,000 to approximately 2 in 2,000 after exposure of 5 rads (15,16). The potential risks and benefits of CT during pregnancy should be discussed with patients. CT contrast seems safe to use in pregnancy and should be administered in the usual fashion (6).
Magnetic Resonance Imaging
In recent years, magnetic resonance imaging (MRI) has been used as a tool to identify the cause of abdominal pain during pregnancy. MRI studies confirm that the appendix and cecum are superiorly displaced as pregnancy advances (17). In one series, MRI was able to correctly identify the appendix in 10 of 12 cases where sonography was uninformative (18). In another study, 29 pregnant women were evaluated with MRI for abdominal or pelvic pain, and correct prospective diagnoses were made in all but one patient (19). More recently, a series of 51 patients were evaluated for abdominal pain with both sonography and MRI. Four cases with appendicitis were found, with three inconclusive results. Ultrasound revealed appendicitis in only two of the confirmed cases. MRI compared favorably with sonography—the overall sensitivity was 100%, specificity 93.5%, and accuracy 94% for detecting appendicitis (20).
According to American College of Radiology guidelines, “Pregnant patients may be approved to undergo MR studies at any stage of pregnancy, so long as the attending radiologist determines the risk–benefit ratio warrants that the study be done” (21). After conferring with the referring provider, the radiologist should document the following:
1. The information from the MR will obtain information not obtainable from nonionizing means
2. The data are needed to affect care given to the patient or fetus during the pregnancy
3. The referring physician does not feel it is prudent to wait to obtain the data until after the patient is no longer pregnant (21).
Gadolinium contrast is not recommended for use in pregnancy. Gadolinium crosses the placenta and enters the fetal circulation. It enters the amniotic fluid, where it is swallowed by the fetus and absorbed (22). It is a pregnancy category C drug, since animal studies have revealed adverse effects but no controlled studies have been performed in humans.
Decisions about contrast use should be made on a case-by-case basis after considering the risks and benefits. Written informed consent for MRI during pregnancy is suggested (21). MRI is not recommended for acute evaluation of severely ill persons, because examinations can be lengthy and there is limited access to patients.
Specific Management
Specific Conditions: Trauma
Trauma complicates 1 in 12 pregnancies. Two thirds of trauma cases in pregnant women are due to motor vehicle crashes, and other common causes are falls, burns, and penetrating wounds. Blunt abdominal trauma is the most frequent mechanism of injury. One percent to 20% of gravidas experience domestic abuse, and up to 60% of women affected report two or more assaults during pregnancy. At one center, nearly 3% of all trauma patients were pregnant, and 11% of these pregnancies were diagnosed during the trauma evaluation (1,23).
Fortunately, severe trauma requiring admission to the ICU is infrequent (3 in 1,000 pregnancies). Maternal death due to trauma is estimated to be 1.9 per 100,000 live births, representing the leading cause of nonobstetric maternal death. It is estimated that 1,300 to 3,900 pregnancies are lost due to maternal trauma each year (24). Mild maternal injuries carry a 1% to 5% fetal loss rate, whereas life-threatening trauma is associated with loss rates up to 40% to 50%. Because mild trauma is more prevalent, most fetal loss is due to minor maternal injury (24). Population-based data indicate that motor vehicle crashes account for 82% of fetal deaths after trauma, with an overall rate of 3.7 per 100,000 live births. The highest rate of fetal death due to trauma is seen in patients between 15 and 19 years of age (25,26).
One study of 271 pregnant women observed after blunt abdominal trauma showed that fetal death was associated with ejection from vehicle, motorcycle crash, pedestrian collision, maternal death, maternal tachycardia, abnormal fetal heart rate (FHR), lack of restraints, and an injury severity score (ISS) greater than 9. Preterm labor was associated with gestational age over 35 weeks, assault, and pedestrian collisions (10). As many as 20% of injured pregnant patients test positive for drugs or alcohol, and one in three do not report using seat belts (27). The worst outcomes take place among those who deliver during their hospital stay for trauma. In this group of patients, the odds ratios (OR) are strikingly high for maternal death (OR 69), fetal death (OR 4.7), uterine rupture (OR 43), and abruption (OR 9.2), compared to women who deliver later or had no trauma (28). Interestingly, fetal survival was 78% among fetuses born to mothers with a high injury severity score (less than 25), whereas maternal survival was only 44%. In contrast, for women with an ISS less than 16, maternal survival was 100% but the fetal survival was only 73%, giving support to the concept that even minor maternal injury places fetuses at risk (29).
Besides fetal death, complications such as abruptio placentae, preterm labor, and fetomaternal hemorrhage can contribute to morbidity and mortality among survivors. The diagnosis of abruption is based on signs and symptoms. One of the best indicators of placental abruption is cardiotocography. In patients with a normal study, the risk of abruption after trauma is approximately 1% to 5%. In patients with more than six contractions per hour or abnormal fetal heart rate patterns, the risk of abruption can be 20% or higher.
All women over 24 weeks' gestation should undergo an initial evaluation with cardiotocographic monitoring for 4 to 6 hours after trauma. Four to 6 hours of observation is sufficient for patients who have experienced minor trauma, and who are hemodynamically stable, with a negative primary evaluation, FAST-US, and reassuring cardiotocography (29). An extended period of observation for 24 hours or more is indicated for women with six or more contractions per hour, nonreassuring FHR patterns, vaginal bleeding, uterine pain or tenderness, premature rupture of membrane (PROM), or serious maternal injury. Consideration for prolonged monitoring is advised if laboratory data are abnormal, such as decreased fibrinogen or a positive Kleihauer-Betke (KB) test. Patients with these characteristics are more likely to experience abruption or other complications (30).
Kleihauer-Betke testing to detect fetomaternal hemorrhage should be considered for patients beyond the first trimester, especially those with Rh-negative status. RhIG 300 µg IM should be administered to all pregnant women with an Rh-negative blood type. Should the KB test be positive, the amount of fetal bleeding can be quantified and additional RhIG administered as necessary. A positive KB test may also be an indicator for adverse pregnancy outcome after trauma. One study reviewed 166 pregnant trauma cases. In 71 of these cases, a KB test was done. The likelihood ratio for preterm labor was 20.8-fold if the KB was positive, whereas clinical assessment did not predict preterm birth accurately (31).
Pregnant women occasionally present with other types of injuries due to trauma to the head, pelvis, or chest. Pelvic fractures, especially those involving the acetabulum, are associated with high maternal and fetal mortality rates. The mechanism of injury and severity influence mortality more than the classification type or trimester of pregnancy (32). Specific management can be complex and requires the coordination of a multidisciplinary team. Penetrating injury is less common during pregnancy than other forms of trauma. In general, the severity of maternal abdominal or vascular injuries may be less than that of nongravid women, but rate of placental injury and fetal loss tends to be high. Management is similar to that of nonpregnant persons, with careful and prompt evaluation of the placenta and fetus.
Specific Conditions: Appendicitis
Acute appendicitis complicates approximately 1 in 1,500 pregnancies, making it the most common indication for nonobstetric surgery during pregnancy. Overall, appendicitis may occur less frequently in gravid patients than in nonpregnant individuals (33).
Although appendicitis occurs in all trimesters, the second trimester is most typical. More than 80% of patients with appendicitis report right lower quadrant pain, irrespective of the trimester (34). Appendicitis can be difficult to diagnose during pregnancy because signs and symptoms can be easily confused with physiologic changes of pregnancy. Nausea and vomiting are common during pregnancy, but not typically associated with pain. Constipation and bowel irregularity, frequent bothersome symptoms of gestation, can be difficult to interpret. Mild leukocytosis is a normal laboratory finding in pregnant women, rendering it of limited value in making the diagnosis of appendicitis. The white blood cell (WBC) count ranges from 5,000 to 15,000 cells/mm3 in the first two trimesters and can be as high as 20,000 cells/mm3 in labor (35,36). The classic triad of obturator, psoas, and Rovsing signs is present in less than one in three pregnant patients (37). Imaging plays an important role in the diagnosis of appendicitis during pregnancy and is discussed above.
Complications may be increased when appendicitis occurs during pregnancy. A delay in diagnosis and treatment over 24 hours was associated with perforation in 14% to 43% of cases in one report (38). In another study, the perforation rate for appendicitis occurring in the first and second trimesters was 31%, but rose to 69% in the third trimester (39). Fetal loss rates as high as 33% and preterm delivery rates of 14% have also been reported in women undergoing appendectomy (40). This underscores the importance of a high index of suspicion in evaluating women with right lower quadrant pain during pregnancy.
When appendicitis is strongly suspected, surgery should be performed as per usual clinical indications. An incision over the point of maximal tenderness is most often recommended. Laparoscopy may be considered as an alternative in patients under 24 weeks' gestation. For patients under 24 weeks' gestation, the uterine size and location of the appendix may reduce access for laparoscopic procedures.
Specific Conditions: Gallstones
Cholelithiasis is common among pregnant women, seen in 3% to 4% of OB ultrasounds. Symptomatic gallstones occur less frequently, in approximately 1 in 1,000 cases. Half or more of patients experience recurrent bouts of biliary colic, making management a challenge. Traditional management consists of intravenous hydration, nothing by mouth or a low-fat diet, analgesics, and antibiotics. Cholecystectomy is required in 1 to 6 per 10,000 pregnancies. Typical indications for surgery include acute cholecystitis (38%), gallstone pancreatitis (28%), common bile duct stone (20%), and refractory pain (18%) (41). Laparoscopy has been used successfully during pregnancy for this indication, as discussed below. Traditional management emphasized deferring surgery for symptomatic cholelithiasis until after delivery. More recent data suggest that relapse of symptoms is common, seen in 38%, and labor induction due to refractory symptoms results in preterm delivery in some cases (42).
Specific Conditions: Adnexal Surgery
The true incidence of adnexal masses during pregnancy is unclear, but it is estimated to be approximately 1 in 200. Simple ovarian cysts compose the vast majority of cases, and most do not require intervention. Adnexal surgery is necessary in 1 in 1,300 pregnancies, typically due to masses greater than 6–8 cm, complex masses, and ovarian torsion. Malignancy is uncommon, seen in less than 10% of cases (43). Care should be taken to avoid removal of the corpus luteum in the first trimester prior to 10 weeks' gestation, as this can result in disruption of the ongoing pregnancy unless progesterone supplementation is provided.
Historically, about half of surgeries performed were due to ovarian torsion (1). With improvements in the diagnosis of ovarian masses, surgery during pregnancy for asymptomatic patients with adnexal pathology has become more common. In one series of 44 cases of benign ovarian masses, most surgeries were performed successfully using laparoscopy in the middle trimester, and the most common diagnosis was benign cystic teratoma (44). Outcomes after adnexal surgery during pregnancy have been shown to be excellent, so long as surgery is performed after the 7th week of gestation (45).
Fetal Assessment
Risk of Fetal Loss and Recommended Fetal Assessment
A review of 55 papers regarding surgery during pregnancy, including 12,452 patients reported in the literature, confirms that the total fetal loss rate is low, at 2.5%. Birth defects after first trimester surgeries occurred in 3.9%, and the miscarriage rate was 5.8%, likely not increased above background rates, but not proven due to lack of controls for comparison. Premature labor after nonobstetric surgery was seen in 3.5%, and the overall rate of preterm birth was 8.2%. The highest risk for preterm birth and fetal loss was seen with appendectomy. In this setting, the preterm delivery rate was 4.6%, and losses occurred in 10.9% of cases (46).
There is no consensus on optimal fetal monitoring in the perioperative period. During the first trimester, no specific fetal evaluation is necessary. Documentation of a live intrauterine pregnancy prior to surgery is prudent in those patients who present with abdominal complaints, primarily to exclude the possibility of ectopic pregnancy or nonviable gestation. From 14 weeks to 24 weeks, assessment of fetal heart tones is advised preoperatively and postoperatively. Perioperative assessment of contractions may be considered after 20 to 24 weeks.
At 24 weeks or beyond, cardiotocography should be performed before and after completion of surgery. In special circumstances, intraoperative monitoring may be chosen. It is important to remember that anesthetic drugs may be associated with decreased fetal heart rate variability, and misinterpretation has led to unnecessary emergency cesarean deliveries (47). In general, if the mother is normotensive and normoxemic, the fetus is well maintained. In the setting of trauma, an initial evaluation consisting of 4 to 6 hours of cardiotocography is warranted, as discussed above.
Decisions about the timing, duration, and methods of fetal monitoring are dependent on the clinical scenario and procedure planned. Such decisions should be made in consultation with an obstetrician and with input from an anesthesiologist.
Preterm Labor and Tocolysis
Preterm labor is a frequent event, due to either the underlying condition or the surgical intervention. In one series of 77 patients undergoing nonobstetric surgery, preterm labor was seen in 26% of patients in the second trimester and in 82% of those in the third trimester. Preterm labor was commonest after appendicitis and adnexal surgery. Actual preterm birth was seen in 16%. Only in 5%, however, was a clear link to the surgical procedure established (1). Another study of 62 pregnant subjects with nonobstetric abdominal surgery during pregnancy revealed 18% delivered preterm, similar to that institution's preterm delivery rate but higher than the national average (48,49).
Most women with preterm labor will not deliver prematurely. Tocolytic medications are given to reduce uterine contractions in many cases, because it is difficult to predict accurately which women will go on to deliver prematurely. There is not a single drug of choice to manage preterm labor. The most commonly used tocolytic agents include nifedipine, magnesium sulfate, and indomethacin. The selection of a tocolytic drug should be based on gestational age, maternal health conditions, and possible side effects. Because tocolytic drugs prolong pregnancy for only 2 to 7 days, their chief utility is to allow for administration of steroids to improve fetal lung maturity (50).
In the postoperative patient, discomfort most often represents typical postsurgical pain, but care should be taken to evaluate for preterm labor or signs of intrauterine infection.
Clinical assessment includes physical examination with palpation of the fundus, cervical examination, and cardiotocography. Adjunctive tests to aid in predicting preterm birth include cervical length measurement, fetal fibronectin testing, and possibly amniocentesis. Tocolysis should be undertaken with caution in the surgical patient, and obstetric consultation is recommended in the event of preterm contractions after surgery.
Corticosteroids for Fetal Lung Maturity Enhancement
All pregnant women between 24 and 34 weeks of gestation who are at risk of preterm delivery within 7 days should be given a single course of corticosteroids for fetal lung maturity enhancement (51).
Recommended regimens for this indication include the following:
· Betamethasone, 12 mg intramuscularly every 24 hours for two doses
· or
· Dexamethasone, 6 mg intramuscularly every 12 hours for four doses
These corticosteroids have been shown to cross the placenta and still retain their biologic effects. They have minimal mineralocorticoid activity and cause little immune suppression. Overall, antenatal corticosteroid use has proved to be one of the most beneficial interventions in the treatment of preterm labor. Corticosteroids for fetal lung maturity enhancement reduce the incidence and severity of respiratory distress syndrome in preterm infants, and betamethasone has been shown to decrease neonatal mortality (52). In addition, intraventricular hemorrhage and necrotizing enterocolitis are decreased with steroid use (52,53). Consideration should be given as to whether a patient may benefit from corticosteroid administration, and decisions individualized. Consultation with an obstetrician regarding this issue is recommended.
Venous Thromboembolism Prevention
Pregnancy is a prothrombotic state, and the risk of venous thromboembolism (VTE) is increased among women who undergo cesarean delivery as compared with vaginal birth (53). However, there are few data regarding the risk for VTE after nonobstetric surgery. There are no clear guidelines or recommendations to address prevention of thromboembolism in the setting of trauma or abdominal surgery during pregnancy. Nonpregnant trauma patients with at least one risk factor for VTE (including estrogen exposure) are recommended to receive thromboprophylaxis (54,55). In the gravid patient, mechanical prophylaxis, such as pneumatic compression, is reasonable, and low-molecular-weight heparin (LMWH) prophylaxis can be considered on a case-by-case basis. For patients with additional risk factors for thromboembolism beyond pregnancy itself, pharmacologic methods should be combined with use of mechanical approaches.
Consultation
Obstetrics
Obstetric consultation should be considered for any patient requiring surgery during pregnancy. Because there are few data to guide clinical management, the American College of Obstetricians and Gynecologists states that “it is important for non-obstetric physicians to obtain obstetric consultation before performing non-obstetric surgery. The decision to use fetal monitoring should be individualized, and each case warrants a team approach to ensure optimal safety for the woman and her baby” (48).
Anesthesia
Prior to delivering anesthesia care, the anesthesiologist is responsible for reviewing the medical record, interviewing and performing a focused examination on the patient, ordering and reviewing appropriate medical tests, ordering appropriate medications, ensuring consent for anesthesia is obtained, and documenting the above in the patient medical record. Preoperative anesthesia consultation should be considered in most cases of nonobstetric surgery during pregnancy, as obstetric complications that may lead to operative delivery are possible (56,57).
Neonatology
In the scenario of surgical diseases affecting third trimester pregnancy, decisions must be made about obstetric and neonatal management. This is especially critical for cases at the threshold of viability. Parents should participate along with physicians in decisions regarding management, including the selection of facility for perinatal care, the type of fetal surveillance planned, and whether or not to perform cesarean birth for fetal indications.
Although the overall prognosis for premature infants has steadily improved, the morbidity and mortality for extremely low-birth-weight infants remains high. The mean survival rates for infants born between 23 and 25 weeks increase from 30%, to 52%, to 76% with each additional week of development. Likewise, the survival for infants weighing 401–800 g ranges from 11% in those under 500 g to 74% in those over 701 g. Severe disability is common among survivors in this group of vulnerable infants.
Neonatal consultation is extremely important for those patients at risk for preterm birth, particularly in the “periviable” period. Parents should be informed about the prospects for infant survival, the likelihood of various outcomes related to prematurity, and the potential risks and benefits of treatments for preterm infants. Decisions regarding the planned level of intervention for the neonate should be documented in the medical record. Noninitiation of resuscitation for newborns less than 23 weeks or 400-g birth weight is appropriate (58).
Perioperative Management
Anesthesia
The goals of anesthesia for nonobstetric surgery are different than those of the labor patient. Instead of attempting to preserve uterine tone and minimize fetal sedation, the objective is to provide effective surgical anesthesia while avoiding stimulating uterine contractions. There is little concern for the effects of fetal respiratory depression, but instead a focus on uteroplacental exchange.
In general, regional or local anesthetics are thought to be safer than general anesthesia. Regional anesthesia for abdominal surgery has the advantage of minimal fetal local anesthetic drug exposure and is less likely to be associated with airway complications. Local anesthetics are not known to be teratogenic when used in this clinical setting.
Due to the risk of aspiration from gastroesophageal (GE) reflux and delayed gastric emptying, it is customary to administer a nonparticulate antacid or H2 blocker as well as medication to improve GE sphincter tone preoperatively. If general anesthesia is planned, preoxygenation and rapid-sequence intubation are typically performed. Care should be taken to avoid hyperventilation, as uterine blood flow is impaired. Inhalational agents, such as isoflurane and others, decrease uterine tone and effectively inhibit labor during surgery.
In general, agents used for general anesthesia during pregnancy, including a single dose of benzodiazepines, nitrous oxide, and inhalational agents, have not been shown to be teratogenic. Fetal loss, low birth weight, and perinatal mortality increases after nonobstetric surgery appear not to be influenced by the choice of anesthetic in one study of 5,405 operations in pregnant women (59).
Laparoscopy during Pregnancy
Various conditions are suitable for treatment via laparoscopic surgery. In general, laparoscopy has had a good record of safety during pregnancy. Special considerations for laparoscopy during pregnancy might include use of an open technique to gain access to the abdominal cavity, direct visualization for trocar placement, and lower insufflation pressures. Laparoscopy is of limited utility in late pregnancy, when the size of the uterus obscures views and reduces access to abdominal structures.
Rates of fetal loss in the first trimester have been reported to be about 10% to 15%, similar to persons with no surgery (60). The effects of CO2 on the fetus are unclear. Insufflation with carbon dioxide has been reported to cause metabolic acidosis in animal studies but is not known to cause harmful sequelae in human cases (60,61).
The largest experience with laparoscopy has been reported by the Swedish Health Registry (2,233 laparoscopies and 2,491 open laparotomies). In both groups, there was an increase in low birthweight (<2,500 g) due to fetal growth restriction and also associated with delivery before 37 weeks. There were no significant differences between the groups with respect to any other obstetric outcomes (62). It would seem reasonable to assess fetal growth periodically among patients who have undergone nonobstetric surgery. Guidelines for laparoscopic surgery during pregnancy are displayed in Table 100.4 (63).
Delivery Considerations
Optimal maternal and infant outcome depends on planning for contingencies. Action items that might impact care when managing pregnant trauma or surgery patients are listed below:
1. Admit the mother to a facility able to provide appropriate specialty care, including neonatology and neonatal intensive care unit (NICU) care.
2. Provide level I trauma center care for any gravid trauma patient whenever possible.
3. Ensure immediate availability of equipment for emergency delivery, in the emergency room (ER), main operating room (OR), intensive care unit (ICU), or surgical unit, where appropriate. This includes all items for infant resuscitation, such as warmer bed, oxygen, endotracheal tubes, suction, other supplies, and emergency medications.
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Table 100.4 Society for American Gastrointestinal Endoscopic Surgeons guidelines for laparoscopic surgery during pregnancy (2000) |
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4. Plan for adequate staff to address obstetric issues, including fetal monitoring and/or emergency delivery.
5. Plan for adequate nursing care for perioperative needs on labor and delivery ward.
6. Ensure that clear instructions designate which providers or specialty services are responsible for various aspects of patient care.
7. Display contact information for the various providers prominently in patient medical record, in case emergency evaluation and treatment is necessary.
8. Encourage impeccable communication between specialists, including general surgery, trauma surgery, obstetrics, anesthesiology, neonatology, or others.
9. Obtain consultations early, and document recommendations or treatment plans.
10. Clearly indicate what the plans are for fetal assessment and whether or not intervention is planned for indications, such as emergent cesarean in the event of nonreassuring fetal heart rate patterns.
11. Delivery timing and route may be individualized. In general, delivery at full term (≥37 weeks) is the goal. Cesarean is reserved for usual clinical indications, with the notable exception of the perimortem patient (Table 100.5).
12. A typical trauma care team for a gravid patient includes the following:
a. ER physician
b. ER nurse
c. Trauma surgeon
d. Obstetrician
e. OB nurse
f. Anesthesiology
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Table 100.5 Iindications For Emergent Cesarean |
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g. Pediatrician available
h. NICU or nursery nurse available
i. OR team on standby
Maternal CPR or Death
Rarely, a pregnant woman is sufficiently unstable to require cardiopulmonary resuscitation (CPR) or advanced cardiac life support (ACLS) procedures. To be most effective with CPR, it is important to recall the physical changes of pregnancy that affect the efficiency of compressions. Aortocaval compression by the gravid uterus decreases cardiac output by 25%, and hypotension in supine position is not uncommon.
The American Heart Association suggests key components for the resuscitation of the pregnant woman in cardiac arrest, itemized below (64):
1. left lateral position
2. 100% oxygen
3. IV access and fluid bolus
4. Identification of the cause of cardiac arrest, and consideration of other medical conditions that could complicate efforts to revive the patient
Chest compressions should be done higher on the sternum, slightly above the center, because of the elevated diaphragm and abdominal contents. Vasopressors should be used when necessary, but be aware that epinephrine, vasopressin, and dopamine can decrease uterine blood flow. Maintaining maternal circulation is still the most important means of supporting the fetus, even in the event of maternal CPR. Medication doses and defibrillation protocols do not change. If fetal or uterine monitors are in place, these should be removed before delivering shocks. No other changes from the ACLS protocol are advised. Pregnancy-specific complications that providers should consider during their resuscitation efforts include magnesium toxicity, eclampsia, and amniotic fluid embolism (64).
Perimortem Cesarean
Intact survival of a fetus is most likely when cesarean delivery is accomplished within 5 minutes of cardiac arrest in a pregnant patient (65). A recent report of outcomes after 38 cases of perimortem cesarean indicated that there were 34 surviving infants. Of those infants, time of delivery was available for 25 cases. Twelve of 25 (48%) were delivered within 5 minutes, and 9 of these 12 infants had no neurologic deficits on follow-up. Of the remaining cases, four were delivered between 6 and 10 minutes, two between 11 and 15 minutes, and seven delivered more than 15 minutes from cardiac arrest. Neurologic sequelae were present in at least one of the survivors in each of these groups. Interestingly, of 20 perimortem cesareans with resuscitable causes, 13 mothers were revived and discharged from the hospital in good condition (65). Clearly there is a role for this life-saving procedure for both mother and baby.
Maternal Brain Death
On rare occasions maternal brain death is identified in a pregnant woman while somatic support has been maintained and the fetus remains alive. Under these circumstances, a determination must be made as to whether to deliver the fetus immediately, to initiate supportive care to allow further fetal maturation, or to allow the fetus to die as the mother is removed from mechanical ventilation. Immediate delivery when gestational age is consistent with neonatal survival is always preferred. However, if the mother's condition permits, it is possible to support the mother and previable fetus until fetal maturation allows for neonatal survival. This somatic support can be provided for extended periods with no apparent neonatal or pediatric sequelae with 2-year follow-up reported (66,67).
Ethical Decision Making
There is a potential for conflicts in decision making between the clinician and the pregnant woman. Patients may be asked to consent to procedures that carry some risk to the fetus. Alternatively, interventions proposed for fetal benefit may present a risk to maternal health. Principle-based ethics, based on the concepts of autonomy, beneficence, and justice, have been used to aid choices. Providers also need to take into account the social and cultural context within which the patient is making her choices. According to the ACOG Ethical Guidelines, “Every reasonable effort should be made to protect the fetus, but the pregnant woman's autonomy should be respected …Intervention against the wishes of a pregnant woman is rarely if ever acceptable” (68).
In the case of a patient who is incapacitated, state laws vary with respect to who may serve as a surrogate decision maker. The designees should base their decisions on the values and wishes of the patient, which may or may not have previously been stated in writing. Clinicians should try to anticipate such scenarios and attempt to adhere to the woman's wishes regarding treatment for herself and/or her fetus. If there is not consensus about who should be designated, the advice of an ethics committee should be considered.
Injury Prevention/Reduction
Lack of seat belt use has been shown to contribute to the severity of maternal and fetal injuries. Knowledge of proper seat belt use is low among some patients, especially teens and those with low education levels. In one survey of 450 pregnant women, only 72.5% reported using the seat belt in the proper location. Women who always wore restraints were more likely to report correct placement. 60% of respondents thought restraints would protect their baby, whereas 11.6% thought restraints caused injury to the baby, and 37% were unsure. The most common reasons for lack of use were lack of comfort (52.8%) and forgetting (42.5%). However, only 36.9% of women reported receiving information about seat belt use during that pregnancy (69). Another survey of 807 women revealed that although 79% of women used safety restraints, only 52% of them did so correctly, and only 21% were educated on proper use during pregnancy (70). Educational interventions during prenatal care can improve the proper use of seat belts significantly. At one institution, the proportion of women reporting correct seat belt placement improved from 70.8% to 83% after instruction during prenatal care (71).
There are case reports of complications due to seat belts and air bags, including uterine rupture (72). However, the evidence to date suggests that correct use of seat belts reduces the likelihood of fetal loss. One statewide study reviewed the experience of 8,928 women (2.8% of the overall pregnant population) with a history of motor vehicle crashes during pregnancy. Unbelted women were 2.8 times more likely to experience a fetal death after the incident (73). Prenatal care visits and emergency room encounters provide an opportunity for providers to give health messages to their patients regarding the importance of proper seat belt use.
Domestic Violence Awareness
Studies indicate that women who experience physical violence are at higher risk for pregnancy loss and low-birth-weight infants (74). A recent prospective study of pregnant women indicated that among 949 surveyed, low birth weight was increased in those reporting verbal abuse (7.6% vs. 5.1%). Also, neonatal deaths were more common among those with physical abuse (1.5% vs. 0.2%). Unexpectedly, 94 women who declined interview had higher rates of low-birth-weight infants (12.8%), preterm birth (5.3% vs. 1.2%), abruption (7.4% vs. 2.2%), and NICU admission (7.4% vs. 2.2%) than those reporting no abuse (75).
Women generally feel that a provider asking them about domestic violence in a confidential, private setting is helpful. Universal screening for domestic violence is recommended by several professional organizations, such as American Medical Association (AMA), American College of Obstetricians and Gynecologists (ACOG), and American Academy of Family Physicians (AAFP). Behavioral cues that domestic violence may be an issue include late entry to prenatal care or sporadic attendance at prenatal visits, changes in appointment patterns, overprotective or threatening partner, or multiple visits for somatic complaints. Battered women are commonly reported to seek medical services at eight times the rate of other women, but they are rarely identified or referred for services. Indeed, battered women account for up to a quarter of all women seeking emergency medical services and/or prenatal care. Emergency visits for abdominal complaints or trauma may serve to prompt the clinician to consider domestic violence as an underlying cause of symptoms. Should a patient indicate that domestic violence is a concern, assistance is available from the National Domestic Violence Hotline, 1-800-799-SAFE. This 24-hour, toll-free hotline provides information and referrals from anywhere in the United States.
References
1. Visser BC, Glasgow RE, Mulvihill KK, et al. Safety and timing of nonobstetric abdominal surgery in pregnancy. Dig Surg. 2001;18:409–417.
2. Pearlman MD, Tintinalli JE, Lorenz RP. A prospective controlled study of outcome after trauma during pregnancy. Am J Obstet Gynecol. 1990;162:1502–1510.
3. Lockitch G, The effect of normal pregnancy on common biochemistry and hematology tests. In: Barron WM, Lindheimer MD, eds. Medical Disorders during Pregnancy. 3rd edn. St. Louis, MO: Mosby; 2000.
4. American College of Obstetricians and Gynecologists. Assessment of risk factors for preterm birth. ACOG Practice Bulletin. October 2001, Number 31.
5. Goldenberg RL, Hauth JC, Andrews WW. Intrauterine infection and preterm delivery. N Engl J Med. 2000;342:1500–1507.
6. American College of Obstetricians and Gynecologists. Guidelines for diagnostic imaging during pregnancy. ACOG Committee Opinion. September 2004, Number 299.
7. Bochicchio GV, Haan, JM, Scalea TM. Surgeon-performed focused assessment with sonography for trauma as an early screening tool for pregnancy after trauma. J Trauma. 2002;52(6):1125–1128.
8. Goodwin H, Holmes JF, Wisner DH. Abdominal ultrasound examination in pregnant blunt trauma patients. J Trauma. 2001;50(4):689–693.
9. Ormsby EL, Geng J, McGahan JP, et al. Pelvic free fluid: clinical importance for reproductive age women with blunt abdominal trauma. Ultrasound Obstet Gynecol. 2005;26(3):271–278.
10. Curet MJ, Schermer CR, Demarest GB, et al. Predictors of outcome in trauma during pregnancy: identification of patients who can be monitored for less than 6 hours. J Trauma. 2000;49(1):18–24.
11. Reis PM, Sander CM, Pearlman MD. Abruptio placentae after auto accidents. A case-control study. J Reprod Med. 2000;45:6–10.
12. Lim HK, Bae SH, Seo GS. Diagnosis of acute appendicitis in pregnant women: value of sonography. Am J Roentgenol. 1992;159:539–542.
13. Stauffer RA, Adams A, Wygal J, et al. Gallbladder disease in pregnancy. Am J Obstet Gynecol. 1982;144:661–664.
14. Lowdermilk C, Gavant ML, Qaisi W, et al. Screening helical CT for evaluation of blunt traumatic injury in the pregnant patient. Radiographics. 1999;19:5243–5255.
15. Castro A, Shipp TD, Castro EE, et al. The use of helical computed tomography in pregnancy for the diagnosis of acute appendicitis. Am J Obstet Gynecol. 2001;184:954–957.
16. Damilakis J, Perisinakis K, Voloudaki A, et al. Estimation of fetal radiation dose from computed tomography scanning in late pregnancy: depth-dose data from routine examinations. Invest Radiol. 2000;35:527–533.
17. Oto A, Srinivasan PN, Ernst RD, et al. Revisiting MRI for appendix location during pregnancy. Am J Roentgenol. 2006;186:883–887.
18. Cobben LP, Groot I, Haans L, et al. MRI for clinically suspected appendicitis during pregnancy. Am J Roentgenol. 2004;183:671–675.
19. Birchard KR, Brown MA, Hyslop WB, et al. MRI of acute abdominal and pelvic pain in pregnant patients. Am J Roentgenol. 2005;184:452–458.
20. Pedrosa I, Levine D, Eyvazzade AD, et al. MR imaging evaluation of acute appendicitis in pregnancy. Radiology. 2006;238:891–899.
21. Kanal E, Borgstede JP, Barkovich AJ, et al. American College of Radiology White Paper on MR Safety. AJR Am J Roentgenol. 2002;178:1335–1347.
22. Kanal E, Borgstede JP, Barkovich AJ, et al. American College of Radiology White Paper on MR Safety: 2004 update and revisions. Am J Roentgenol. 2004;182:1111–1114.
23. Bochicchio GV, Napolitano LM, Haan J, et al. Incidental pregnancy in trauma patients. J Am Coll Surg. 2001;192(5):566–569.
24. American College of Obstetricians and Gynecologists. Obstetric aspects of trauma management. ACOG Educational Bulletin. September 1998, Number 251.
25. Horon IL, Cheng D. Enhanced surveillance for pregnancy-associated mortality—Maryland 1993–1998. JAMA. 2001;285:1455–1459.
26. Weiss HB, Songer TS, Fabio A. Fetal deaths related to maternal injury. JAMA. 2001;286:1863–1868.
27. Ikossi DG, Lazar A, Morabito D, et al. Profile of mothers at risk: an analysis of injury and pregnancy loss in 1,195 trauma patients. J Am Coll Surg. 2005;200(1):49–56.
28. El-Kady D, Gilbert W, Anderson J, et al. Trauma during pregnancy: an analysis of maternal and fetal outcomes in a large population. Am J Obstet Gynecol. 2004;190(6):1661–1668.
29. Curet MJ, Schermer CR, Demarest GB, et al. Predictors of outcome in trauma during pregnancy: identification of patients who can be monitored for less than 6 hours. J Trauma. 2000;49:18–25.
30. Goodwin TM, Breen MT. Pregnancy outcome and fetomaternal hemorrhage after noncatastrophic trauma. Am J Obstet Gynecol. 1990;162:665–671.
31. Muench MV, Baschat AA, Reddy UM, et al. Kleihauer-Betke testing is important in all cases of maternal trauma. J Trauma. 2004;57(5):1094–1098.
32. Leggon RE, Wood GC, Indeck MC. Pelvic fractures in pregnancy: factors influencing maternal and fetal outcomes. J Trauma. 2002;53(4):796–804.
33. Andersson REB, Lambe M. Incidence of appendicitis during pregnancy. Int J Epidemiol. 2001;30:1281–1285.
34. Mourad J, Elliott JP, Erickson L, Lisboa L. Appendicitis in pregnancy: new information that contradicts long-held clinical beliefs. Am J Obstet Gynecol. 2000;182:1027–1029.
35. Martin C, Varner MW. Physiologic changes in pregnancy: surgical implications. Clin Obstet Gynecol. 1994;37:241–255.
36. Delgado I, Neubert R, Dudenhausen JW. Changes in white blood cells during parturition in mothers and newborns. Gynecol Obstet Invest. 1994;338:227–235.
37. Tamir IL, Bongard FS, Klein SR. Acute appendicitis in the pregnant patient. Am J Surg. 1990;160:571–575.
38. Bickell NA, Siu AL. Why do delays in treatment occur? Lessons learned from ruptured appendicitis. Health Serv Res. 2001;36:1–5.
39. Weingold AB. Appendicitis in pregnancy. Clin Obstet Gynecol. 1983;26:801–809.
40. Andersen B, Nielsen TF. Appendicitis in pregnancy: diagnosis, management, and complications. Acta Obstet Gynecol Scan. 1999;78:758.
41. Cosenza CA, Saffari B, Jabbour N, et al. Surgical management of biliary gallstone disease during pregnancy. Am J Surg. 1999;178:545–548.
42. Lu E, Curet M, El-Sayed Y, et al. Medical versus surgical management of biliary tract disease in pregnancy. Am J Surg. 2004;188:755–759.
43. Kort B, Katz VL, Watson WJ. The effect of nonobstetric operation during pregnancy. Surg Gynecol Obstet. 1993;177:371–376.
44. Ishihara Y, Inoue H, Kohata Y, et al. Delivery outcomes following laparoscopic ovarian cystectomy during pregnancy. Gynecol Endosc. 2002;11:417–421.
45. Wang PH, Chao HT, Yuan CC, et al. Ovarian tumors complicating pregnancy. Emergency and elective surgery. J Reprod Med. 1999;44:279–287.
46. Cohen-Kerem R, Railton C, Oren D, et al. Pregnancy outcome following non-obstetric surgical intervention. Am J Surg. 2005;190:467–473.
47. Immer-Bansi A, Immer FF, Henle S, et al. Unnecessary emergency cesarean section due to silent CTG during anesthesia? Br J Anaesth. 2001;87:791–793.
48. American College of Obstetricians and Gynecologists. Nonobstetric surgery during pregnancy. ACOG Committee Opinion. August 2003 Number 284.
49. Gerstenfeld TS, Chang DT, Pliego AR, et al. Nonobstetrical abdominal surgery during pregnancy in Women's Hospital. J Matern Fet Med. 2002;9:170–172.
50. American College of Obstetricians and Gynecologists. Management of preterm labor. ACOG Practice Bulletin. May 2003, Number 43.
51. American College of Obstetricians and Gynecologists. Antenatal corticosteroid therapy for fetal maturation. ACOG Committee Opinion. May 2002, Number 273.
52. Roberts D, Dalziel S. Antenatal corticosteroids for accelerating fetal lung maturation for women at risk of preterm birth. Cochrane Database Syst Rev. 2006 Jul 19;3:CD004454.
53. Ballard PL, Ballard RA. Scientific basis and therapeutic regimens for use of antenatal corticosteroids. Am J Obstet Gynecol. 1995;173:254–262.
54. Greer IA. Thrombosis in pregnancy: maternal and fetal issues. Lancet. 1999;353:1258–1265.
55. Geerts WH, Pineo GF, Heit JA, et al. Prevention of venous thromboembolism: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy. Chest. 2004;126:338S–400S.
56. Basic standards for preanesthesia care. American Society of Anesthesiologists, 2005.
57. American College of Obstetricians and Gynecologists. Obstetric analgesia and anesthesia. ACOG Practice Bulletin. July 2002, Number 36.
58. MacDonald H. American Academy of Pediatrics, Committee on Fetus and Newborn. Perinatal care at the threshold of viability. Pediatrics. 2002;110:1024–1027.
59. Maze RI, Kallen B. Reproductive outcome after anesthesia and operation during pregnancy: a registry study of 5405 cases. Am J Obstet Gynecol. 1989;161:1178–1185.
60. Rizzo AG. Laparoscopic surgery in pregnancy: long-term follow-up. J Laparoendosc Adv Surg Tech. 2003;13(1):11–15.
61. Hunter JG, Swanstrom L, Thornburg K. Carbon dioxide pneumoperitoneum induces fetal acidosis in a pregnant ewe model. Surg Endosc. 1995;9:272–279.
62. Reedy MB, Kallen B, Kuehl TJ. Laparoscopy during pregnancy: a study of five fetal outcome parameters with the use of the Swedish Health Registry. Am J Obstet Gynecol. 1997;177:673–679.
63. SAGES publication 0023, 2000. SAGES guidelines for laparoscopic surgery during pregnancy. www.sages.org/sagespublication.php?doc=23. Accessed October 22, 2006.
64. American Heart Association. Cardiac arrest associated with pregnancy. Circulation. 2005;112:IV-150–IV-153.
65. Katz V, Balderston K, DeFreest M. Perimortem cesarean delivery: were our assumptions correct? Am J Obstet Gynecol. 2005;192:1916–1921.
66. Powner DR, Bernstein IM. Extended somatic support for pregnant women after brain death. Crit Care Med. 2003;31:1241–1248.
67. Bernstein IM, Watson M, Simmons GM, et al. Maternal brain death and prolonged fetal survival. Obstet Gynecol. 1989;74:434–437.
68. American College of Obstetricians and Gynecologists. Patient choice in the maternal-fetal relationship. Ethics in Obstetrics and Gynecology. 2nd ed. www.acog.org. Accessed October 22, 2006.
69. McGwin G, Russell SR, Rux RL, et al. Knowledge, beliefs, and practices concerning seat belt use during pregnancy. J Trauma. 2004 Mar;56(3):670–675: beliefs and practices. J Trauma. 1999 Feb;46(2):241–245.
70. McGwin G Jr, Willey P, Ware A, et al. A focused educational intervention can promote the proper application of seat belts during pregnancy. J Trauma. 2004;56(5):1016–1021.
71. Astarita DC, Feldman B. Seat belt placement resulting in uterine rupture. J Trauma. 1997;42:738–740.
72. Hyde LK, Cook LJ, Olson LM, et al. Effect of motor vehicle crashes on adverse fetal outcomes. Obstet Gynecol. 2003;102(2):279–286.
73. Murphy CC, Schei B, Myhr T, et al. Abuse: a risk factor for low birth weight? A systematic review and meta-analysis. Can Med Assoc J. 2001;164:1567–1572.
74. Yost NP, Bloom SL, McIntire DD, et al. A prospective observational study of domestic violence during pregnancy. Obstet Gynecol. 2005;106:61–65.