Catherine Takacs Witkop1
(1)
Department of Obstetrics/Gynecology and Preventive Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, USA
Catherine Takacs Witkop
Email: cwitkop@gmail.com
Abstract
Overweight and obesity are risk factors for several labor and postpartum complications, including macrosomia, shoulder dystocia, and cesarean delivery. Anesthesia and surgical intervention also present unique challenges, but research has provided new insights on how to reduce complications in these two areas. Providers can use currently available evidence to counsel patients, and this conversation should begin during the prenatal period. Further research is needed to address the gaps in our understanding of the most effective methods of delivery and postpartum care for overweight and obese women.
Keywords
OverweightObesePregnancy outcomesLaborDeliveryCesarean delivery
“Pregnancy presents an opportunity for women to develop skills to be engaged, savvy, knowledgeable consumers …”Amy Romano, “The First National Maternity Care Shared Decision Making Initiative,” (www. Informedmedicaldecisions.org)
Key Points
· Overweight and obesity increase the risk of maternal and newborn complications during labor, delivery, and the immediate postpartum period.
· Shared decision making acknowledges that a woman’s values and preferences will influence her decisions for care during labor and assist in assessing the balance of benefits and harms of treatment decisions.
· Labor patterns in overweight and obese women differ from patterns in normal-weight women and may account for the higher incidence of cesarean delivery in overweight and obese women.
· Overweight and obese women are at increased risk for anesthetic complications, but adequate anesthesia is critical during labor, given the increased chance of cesarean delivery.
· Cesarean delivery in the obese parturient can pose unique surgical challenges for the obstetrician, but some preventive measures have been shown to help reduce complications.
Introduction
Overweight and obese women face a number of potential complications in labor that are directly or, in some cases, indirectly related to their weight. Studies have demonstrated that not only are there more adverse outcomes in overweight and obese women but that the risks increase proportionately with extent of overweight [1]. When considering the entire population of overweight and obese women, potential complications can include an increased risk of preeclampsia, gestational diabetes, large for gestational age (LGA) or macrosomic infants, antepartum stillbirth, instrumental delivery, shoulder dystocia, cesarean delivery, intraoperative and postoperative complications, difficulty with anesthesia, meconium aspiration, fetal distress, and early neonatal death [1–4].
Information about these risks is best shared with reproductive-aged women during preconception counseling appointments. If an overweight or obese woman conceives, the next intervention opportunity is during her prenatal care, preferably during the first trimester. However, as seen in the previous chapter, antenatal interventions to limit gestational weight gain within the recommended range are often challenging to implement. Even if the patient does not gain excessive weight during pregnancy, it appears many of the complications are associated with prepregnancy weight. That leaves the obstetric provider with the complex task of managing labor and delivery in a patient who is vulnerable to a number of complications. As will become clear, the evidence demonstrates that there is not a straightforward algorithm for labor management in overweight or obese patients. A decision to avoid one set of potential complications leads to the possibility of a host of others.
Shared decision making is an approach that is being used increasingly in many areas of clinical medicine, in particular, for complex decisions about screening or treatment options. One goal of shared decision making is to provide the patient with the information and tools to help her understand the state of the evidence related to the topic. Even more importantly, this approach acknowledges that a patient’s values and preferences will impact her decisions during her pregnancy, especially when risks and benefits are such that significant uncertainty about outcomes remains.
Because of the twenty-first-century nature of this problem, the medical literature is not replete with prospective studies on management of labor and delivery in the obese patient. But the obesity epidemic is not going away. And until high-quality prospective studies help inform appropriate prenatal or intrapartum interventions, management will rely primarily on available evidence from observational studies, which are unfortunately limited in scope.
Risks of Labor Complications
Overweight and obese women, even those who have normal glucose tolerance, have an increased risk of delivering an infant that is macrosomic [4]. This introduces a number of potential complications during labor and delivery including increased incidence of cesarean or instrumental delivery and increased risk of shoulder dystocia, perineal lacerations (in particular, third- and fourth-degree lacerations), and postpartum hemorrhage.
What is the risk of macrosomia in overweight or obese women? In a prospective, multicenter database study of 16,102 patients, the incidence of macrosomia (as defined as birth weight over 4,000 g) was 14.6 % in morbidly obese women and 13.3 % in obese women as compared to 8.3 % in women with BMI less than 30 kg/m2 [4]. Teasing out the independent risk of obesity versus gestational diabetes, which is more likely in obese women, can be a challenge, but has been attempted. The risk of a macrosomic or large for gestational age (LGA) infant (newborn weight greater than the 90th percentile for gestational age at the institution where the study was performed) was higher in women with pregestational diabetes (OR 4.4), but the risk in nondiabetic obese women was still significant (OR 1.6) in multivariate analysis [5]. In another study of nondiabetic women, prepregnancy weight had the strongest correlation with neonatal fat and body fat percentage in the infant, regardless of glucose tolerance [6]. Based on these and several other studies, it does appear that obesity is independently associated with macrosomia.
Obese women also have a higher risk of shoulder dystocia and birth trauma than normal-weight women, but, again, whether obesity is an independent predictor of shoulder dystocia has been debated. In one study of 9,667 vaginal deliveries, obese women still had a 2.7-fold risk of shoulder dystocia, even after adjustment for macrosomia and diabetes [7]. The most significant risk factors for shoulder dystocia were, however, noted to be macrosomia and diabetes. Cedergren et al. also demonstrated that obesity was an independent risk factor for shoulder dystocia [1].
Since a study over 25 years ago, many have held that a certain threshold of estimated fetal weight provides sufficient support to perform an elective cesarean delivery [8]. In that study by Spellacy et al., women with macrosomic infants (over 4,500 g) were more likely to have cesarean delivery, and the infants had more birth trauma and shoulder dystocia, lower Apgar scores, and higher death rates [8]. In the group with the triad of obesity, diabetes, and postdates, the macrosomia frequency was 5–14 %. Shoulder dystocia occurred significantly more frequently in patients with fetal weight of 4,500–4,999 g (7.3 %) and those over 5,000 g (14.6 %). In that paper, the authors recommended that “women at risk should be screened for macrosomic infants, and if found, they should be delivered electively by cesarean section” [8]. A second study by Lipscomb and colleagues demonstrated an 18.5 % incidence of shoulder dystocia in macrosomic (4,500 g) vaginal deliveries, and women with diabetes had a significantly higher incidence (50 %) than nondiabetic women (13.3 %) [9]. Based primarily on this evidence, the American College of Obstetricians and Gynecologists (ACOG) has recommended that cesarean delivery be considered for pregnancies without diabetes but with a fetus with an estimated fetal weight greater than 5,000 g. Women with gestational diabetes and an estimated fetal weight of >4,500 g should also discuss cesarean delivery with their providers [10].
This recommendation is complicated by the fact that estimating fetal weight in general is a difficult task. Ultrasound is the primary modality to estimate fetal weight, but concerns about using ultrasound to estimate fetal weight arose partly because of studies that showed decreased visualization of fetal structures in obese women. In one study, in patients with BMI in the 97.5th percentile (BMI of 49.4 kg/m2), only 63 % of anatomic structures were visualized [11]. Visualization was slightly better (79.3 %) in women with BMI above 90th percentile (BMI of 36.21 kg/m2) but was still significantly worse than that in normal-weight women and that in women with BMI less than the 10th percentile. In the thinnest women, 90.2 % of the anatomic structures could be visualized [11].
However, in a more recent study, the accuracy of clinical estimation of fetal weight was evaluated across BMI categories [12]. The sensitivity and specificity were 9.7 and 96.6 % for predicting neonatal birth weight greater than the 90th percentile and were not affected by maternal BMI. It would appear that using ultrasound to estimate fetal weight in overweight and obese women can be supported by current evidence, but providers and patients need to understand the risks in making decisions based on estimated fetal weight.
Delivery decisions in the setting of suspected macrosomia can be among the most complex that will be made in the prenatal period. The counseling should occur during the prenatal period, with adequate time to answer questions and allow for the patient to make an informed decision with which she is comfortable. Decision tools are now available that outline questions for the patient to ask herself and her provider regarding the options when complex decisions are to be made. Management of suspected macrosomia is one such situation where providing the patient with such tools could be helpful. For example, induction of labor is not indicated for macrosomia, but patients may come to prenatal appointments requesting induction. Extensive counseling with an informed patient (i.e., one who has received relevant evidence-based information beforehand) is also recommended before making a decision about performing an elective cesarean delivery in the setting of suspected macrosomia. This discussion should not be delayed until the patient is in labor.
Walking a patient through the uncertainty that exists for these decisions and understanding her values and preferences optimizes the decision-making process. She needs to know that some cesarean deliveries will be performed needlessly and vaginal delivery may still result in shoulder dystocia. Furthermore, there is currently no evidence-based recommendation for elective cesarean delivery specifically for obese women.
Labor Management
Management of labor in the overweight or obese patient needs to be undertaken with a great deal of preparation. One author recommends that obstetric units that care for extremely obese pregnant patients develop a “bariatric protocol” and ensure appropriate beds, intraoperative equipment, and supplies are available [13]. ACOG also recommends specific resources, including additional blood products, a large operating table, and enough personnel to assist with the potential complications that may ensue [2]. Given the current obesity epidemic, it is prudent for most obstetric wards to have such a protocol. Table 4.1provides a reasonable checklist, compiled from several sources, for a labor and delivery suite where obese patients may deliver. This checklist can be modified, depending on the practice environment and patient population. For example, accommodating the extremely obese patient can pose additional challenges. Some of the issues related to this population are discussed later in the chapter.
Table 4.1
Checklist for equipment to support obese pregnant patients [2, 13, 14]
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Bariatric bed (600–1,000 lb capacity; 42–54 in width), with frame and trapeze for mobility |
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Chairs in room without sides |
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Bariatric operating table (600–1,000 lb capacity) |
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Larger belt or straps for securing legs to table |
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Toilet capable of accommodating 500+ pounds |
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Inflatable mattress |
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Extra-wide wheelchairs (400–700 lb capacity; 20–30 in width) |
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Extra-large inflatable sequential pneumatic compression devices |
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Bariatric surgical tray (for BMI >40 kg/m2) |
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Extra-long surgical instruments |
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Bookwalter self-retaining retractor |
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Long clamps |
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Appropriate size blood pressure cuff (or thigh cuff) |
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Ability to achieved central venous access if peripheral IV not feasible |
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Ability to place arterial line |
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Access to blood products (blood typed and crossed for transfusion) |
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Appropriate gown sizes |
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Extra personnel in delivery room |
Labor in obese women has been shown to vary from that of normal-weight women, so standard provider expectations for cervical dilation and the threshold for cesarean delivery may need to be adjusted. In one observational study of 509 nulliparous patients, the rate of cervical dilation was inversely proportional to maternal weight [15]. In another study of nulliparous women, duration of labor was significantly longer for overweight and obese women than for normal-weight women, even when adjusting for other potential confounders, such as induction, oxytocin use, epidural analgesia, maternal weight gain, and fetal size [16]. In that study, the median duration of labor from 4 to 10 cm was 7.9 h for obese women, 7.5 h for overweight women, and 6.2 h for normal-weight women [16]. The etiology of the longer labor is not clear but does not appear to be the strength of uterine contractions. When intrauterine pressure was measured in 71 women during the second stage of labor, there was no difference in uterine contractility between three groups of women (normal, overweight, and obese women), although obese women labored longer during the active phase and a BMI greater than 25 kg/m2 was associated with a higher frequency of the need for oxytocin augmentation [17]. Future studies should examine reasons for the difference in labor patterns between women of different weight classifications. One hypothesis relates to increased soft tissue deposits in the pelvis of obese women, but this has not been demonstrated.
For practical purposes, however, clinicians need to understand that labor patterns may be dissimilar in overweight and obese women and thresholds for interventions (or lack of interventions) may need to be adjusted accordingly. An individualized approach to the overweight and obese parturient may result in fewer cesarean deliveries and the complications that might result. Additional challenges that may be encountered when an overweight or obese patient is laboring, include difficulty in monitoring the fetus and the contractions. A fetal scalp electrode and intrauterine pressure catheter may be needed to help guide labor management, especially in a patient with other complications during labor. Cardiovascular issues are also more common in obese women, and more intensive monitoring may be required than with normal-weight women.
Induction of Labor
With an increase in rates of labor induction for both medical and nonmedical indications, the risk-benefit ratio of induction specifically found in the overweight and obese population must be examined. The concepts of shared decision making discussed above are also applicable here. In situations where a medical indication exists for induction of labor, the benefits likely exceed the risks. However, elective induction of labor should not be undertaken without a candid discussion with the patient about risks and benefits, in a way she understands.
In a secondary analysis of a study in which women randomly received cervical ripening with 10 mg dinoprostone, 50 μg misoprostol, or 100 μg misoprostol, the median dose and duration of oxytocin required before delivery (3.5 units and 7.7 h) were significantly greater in obese women and extremely obese women (5.0 units and 8.5 h) as compared to the dose and duration (2.6 units and 6.5 h) in “lean” women (BMI less than 30 kg/m2) [18]. Furthermore, median time to delivery (27.0 h) was significantly longer in the extremely obese group (BMI over 40 kg/m2) than the “lean” group (22.7 h) [18].
The relationship is not clear-cut, however. In another retrospective cohort study of 29,224 women with prolonged pregnancy (defined as 41 and 3/7 weeks’ gestation or longer), there was no association of in length of labor, incidence of postpartum hemorrhage, shoulder dystocia, and neonatal outcomes with weight [19]. Obese women did have a significantly higher rate of cesarean delivery. For women undergoing their first delivery, the cesarean delivery rate was 38.7 % in obese women versus 23.8 % in normal-weight women. Future studies should also continue to examine labor patterns in overweight and obese women and how they differ from normal-weight women, so that abnormal labor can be better characterized and recommendations made for management of labor. Until then, providers should help the patient understand the evidence that exists and help her make an informed decision about undertaking elective induction of labor.
Cesarean Delivery
Given the growing epidemic of obesity and the increasing cesarean delivery rate, it is important to understand the relationship between obesity and risk of cesarean delivery. Both obesity and cesarean deliveries impact the public health. In a systematic review of 11 cohort studies specifically focused on nulliparous patients, the risk of cesarean delivery was increased by 50 % in women with BMI between 25 and 30 kg/m2, and the risk in women with BMI over 30 kg/m2 was more than twice that in women with normal BMI [3]. Although not included in that systematic review, a large population-based study reflected the findings from the review: in the population of nulliparous patients, the rate of cesarean delivery was 20.7 % for the normal BMI group, 33.8 % in the obese group, and 47.4 % for morbidly obese patients (≥35 kg/m2) [4]. In another prospective, population-based cohort study, 3,480 women with body mass index (BMI) over 40 kg/m2 had an increased risk of cesarean delivery, and women with BMI between 35.1 and 40 kg/m2 also demonstrated similar associations, but to a slightly lesser extent [1].
With the rapidly increasing numbers of obese and morbidly obese women, another population is growing in size, the extremely obese women (BMI ≥50 kg/m2). In a retrospective cohort study of 64,272 obese women, extremely obese women were found to have a number of worse outcomes, including higher risk of preeclampsia, macrosomia, cesarean delivery, neonatal hypoglycemia, neonatal length of stay greater than 5 days, and worse composite neonatal score [20]. Interestingly, in this population, 49.1 % of extremely obese women delivered by cesarean delivery (33.8 % of the extremely obese women had scheduled primary cesarean). The indications for the scheduled primary cesarean sections were not clear from this study, and the authors recommended further study to evaluate reasons for such high rates of elective cesarean delivery.
Anesthesia
Providers caring for overweight and obese women need to address potential anesthetic concerns, preferably before labor ensues. It should be standard practice to obtain an anesthetic consultation before planned cesarean section in an obese woman, and it is highly recommended in all obese women during the prenatal period, even if cesarean delivery is not scheduled. This is to account both for pain management during labor as well as to evaluate the patient to prepare for a possible difficult airway in the event of the need for general anesthesia.
In general, regional anesthesia is recommended for the overweight or obese patient in labor or for cesarean delivery. The identification of the epidural space in pregnant women, and particularly in overweight and obese women, can be extremely difficult. Even in the most controlled circumstance, for example in preparation for a scheduled cesarean delivery, complications are a possibility. In a cohort study of women undergoing elective scheduled cesarean delivery, women with BMI 50 kg/m2 or greater were most likely to have complications: 4 % had insufficient duration, 6 % required general anesthesia, and 3 % demonstrated intraoperative hypotension [21]. Overall anesthetic complications were 8.4 % in the extremely obese population as compared to 0 % in the normal-weight women [21]. It is important to counsel patients that such complications can also occur in a controlled, non-emergent situation, such as for an elective cesarean delivery. Decisions to perform elective procedures should not be made lightly.
Although not specifically focused on obese women, studies by Grau on the use of ultrasound to assist in skin-epidural space detection may be of utility in patients with difficult landmarks [22]. In one randomized controlled study of 300 parturients, women in the study group (who underwent ultrasonography for the identification of intervertebral structures and to determine depth and angle for placement of Tuohy needle) had fewer puncture attempts and were more likely to have complete analgesia and lower VAS (visual analog scale) pain score than those in the control group (typical placement without ultrasound). Ultrasound added 75 s to the mean preparation time. The rate of side effects (also including postpartum headache and backache) was lower, and patient acceptance was higher in the study group [22].
Ultrasound guidance is not without risk, as measurements may differ by millimeters between the image and actual depth. Anesthetic providers should still use standard procedures (e.g., loss of resistance (LOR) technique) to assist in placement of the epidural catheter. Obstetric providers may wish to discuss the option of ultrasound-guided epidural placement with anesthesia colleagues, especially for care of overweight and obese patients in their practices.
Regardless of the method used, discussing the benefits of epidural placement early in labor is worthwhile. Given the significantly increased risks of general anesthesia, such as difficult endotracheal intubation and intraoperative respiratory events, it is highly recommended that regional anesthesia is performed in a controlled setting without time pressures [2]. An obese patient without an epidural who requires an emergency cesarean delivery will likely require general anesthesia, resulting in potential further morbidity. Combined spinal-epidural is an ideal solution in an obese patient in labor, or spinal alone can be considered for the patient preparing for cesarean delivery.
Surgical Issues
Overweight and obese women may have an increased risk of intrapartum and postpartum hemorrhage, longer operative times, thromboembolic complications, postpartum endometritis, and wound infection [2]. Obese women undergoing cesarean delivery, whether elective, indicated, or emergency, are at increased risk for infectious complications [23]. Obese patients in one study were more likely to develop endomyometritis and wound infection, even if they received prophylactic antibiotics [23]. BMI and maternal obesity, in addition to length of labor and number of digital cervical examinations, remained significantly associated with infectious morbidity, even after multivariate analysis [23]. Based on their data, the authors recommend providers attempt to shorten labor to less than10 h and perform fewer than four digital exams in obese and overweight women to reduce risk of infection.
A broad-spectrum antibiotic, such as a first-generation cephalosporin, should be administered within 60 min preceding the skin incision. One consideration in extremely obese women is whether there is adequate tissue penetration. There have been no adequate studies in pregnant women to determine the correct dosing for overweight or obese women, but a recent study estimating the adequacy of antimicrobial activity of preoperative antibiotics found that cefazolin concentrations within adipose tissue obtained at skin incision were inversely proportional to maternal BMI [24]. Furthermore, in this study of women undergoing scheduled cesarean delivery who received 2 g of cefazolin at least 30 min before skin incision, a significant proportion of obese and extremely obese women did not have minimal inhibitory concentrations in adipose tissue when sampled at opening and closing of the incision [24]. Common practice is to administer 2 g of cefazolin in obese women (e.g., when BMI is >30 kg/m2) [2]. More studies are clearly needed to determine adequate dosing of antibiotics or the utility of adding a second antibiotic in this high-risk population.
Performing a cesarean delivery on an obese woman requires a clear understanding of anatomic relationships and a skilled surgeon to reduce operative complications. Obese women will often have a significant panniculus that needs to be taken into account in order to effectively deliver the infant in a safe and expeditious manner. Furthermore, obese women who undergo cesarean delivery are more likely than their normal-weight counterparts to have increased likelihood of wound breakdown and infection. There are differing opinions about the benefits of vertical versus horizontal skin incision, but there have been no prospective randomized trials to guide surgeons in this decision. The traditionally stated disadvantage to Pfannenstiel is reduced exposure and potentially more difficulty in delivering a macrosomic infant and difficulty in managing wound breakdown or infection after Pfannenstiel incision.
Several retrospective studies have attempted to answer this question. The incidence of wound complications was 12 % in one retrospective study, and the incidence of wound complications was greater (35 % vs. 9 %) in women with vertical skin incisions [25]. In another smaller case–control study, however, there were no differences in infections or other complications between women undergoing supraumbilical versus Pfannenstiel incisions [26]. In a large multicenter cohort study that examined only emergency cesarean deliveries (2,498 women in all), a vertical incision was found to reduce delivery incision-to-delivery interval by 1 min for primary and by 2 min for repeat cesarean but was associated with more frequent endometritis and postpartum transfusion [27].
Based on the evidence that is available, Pfannenstiel incision can be recommended in most cases, and an incision in the lower abdomen below the panniculus appears to be the ideal approach [29]. The panniculus needs to be retracted cephalad and held in place to ensure visualization, but close attention must be paid to ensure this does not cause respiratory compromise [13]. The other option is to make a higher transverse periumbilical (either supra- or infraumbilically, depending on the body habitus) incision above the panniculus which can be retracted inferiorly if needed. This approach has the advantage of creating the incision where there is the least amount of subcutaneous adipose tissue [25, 27]. Regardless of the approach, a vacuum extractor should be available in the room in the event of difficult delivery of the vertex in an obese woman with limited visualization.
Studies have also focused on closure techniques that could reduce postoperative complications such as wound dehiscence and infection. Closure of the fascia should follow routine procedures, using no. 1 or no. 2 delayed monofilament suture [e.g., polydioxanone (PDS)]. Some experts recommend a Smead-Jones “mass” closure if a vertical incision has been made [13]. The use of a subcutaneous stitch has been more controversial but can be recommended based on a meta-analysis of six studies on this topic that showed there was a significant decrease in wound disruption (which seems to be as a result of decrease in wound seromas) [28, 30]. Moreover, in women with subcutaneous adipose tissue thickness of greater than 2 cm, there was a 34 % (RR 0.66) (risk reduction of 6.2 %) decrease in risk of wound disruption in women [28, 30]. There are no known risks to placing a subcutaneous stitch, other than prolonging operating time, and therefore should be considered in overweight and obese women. The placement of drains has been similarly studied. Research has not demonstrated a clear advantage to using a drain to reduce infectious morbidity [30, 31], nor have studies adequately demonstrated any significant risks with the placement of such a drain. This decision should be left up to the surgeon, although there is not clear evidence indicating its use.
Postoperative and Postpartum Complications
Overweight and obese women are at increased risk for thromboembolic complications. As a result, consideration should be given to preventive measures, especially in women who have undergone a surgical procedure that will reduce postpartum ambulation. Options include pharmacologic interventions and physical measures such as compression stockings and intermittent pneumatic compression. Given the increased risk of venous thromboembolism in this population, all overweight or obese women should have pneumatic compression devices placed before surgery (unless already receiving pharmacologic prophylaxis) [2]. The more difficult question is: when to use pharmaceutical thromboprophylaxis? A systematic review of 13 trials, involving 1,774 women, examined a range of methods of thromboprophylaxis in pregnant women [31, 32]. Unfortunately, the authors concluded that there is insufficient evidence on which to base recommendations. A 2006 consensus panel of experts also reviewed the evidence and determined that, although obese women have a higher incidence of complications in pregnancy, the evidence cannot currently support prescribing heparin or low-dose aspirin to high-risk obese patients who have not had a venous thromboembolism [32, 33]. The panel did suggest that, because multiple studies have demonstrated a possible impact on prothrombotic risk, providers may consider screening obese women for common thrombophilic mutations [32, 33]. There are currently no data supporting this practice. However, providers should keep in mind that obese women are at increased risk and this association might tip the balance toward thromboprophylaxis, especially when another risk factor is present.
It is critical to remember that dosing of thromboprophylactic medications (and also when used for therapeutic purposes) is impacted by weight. Therefore, for appropriate care of overweight and obese patients who require thromboprophylaxis for other indications, providers need to be familiar with weight-based dosing of these medications.
Vaginal Birth After Cesarean (VBAC)
With cesarean deliveries making up 32.8 % of all deliveries in the USA, the issue of delivery management in obese women with previous cesarean delivery is one of great public health importance [33, 34]. Complications of both vaginal delivery and cesarean delivery are higher in overweight and obese women than in normal-weight women, so deciding on the appropriate mode of delivery can be a challenge. Providers have a vital role in educating patients about the risks and benefits of each route and assisting patients in their decisions. In a prospective observational study of obese women (defined as over 300 lb) with history of cesarean delivery, the success rate of vaginal birth after cesarean (VBAC) among the 30 women who underwent trial of labor (TOL) was 13 % (due to arrest of labor, “fetal distress,” and failed induction) as compared to the overall rate of TOL success of 65 % in the institution where the study was conducted [34, 35]. Furthermore, endometritis rates were higher in the trial of labor group [34, 35]. In a subsequent, retrospective study of VBAC success by weight class, examining data in the same institution, the TOL success rate was only 13.3 % in the heaviest women (over 300 lb), which was significantly different from the 81.8 % success rate in the group of women who were less than 200 lb at delivery [35, 36]. Infectious morbidity (including both endometritis and wound infection) was also significantly more common in the group of women over 300 lb. These studies, however, may not be representative of the overall population. In larger, prospective, multicenter study, the VBAC rates were higher, 70 %, but still lower than that in nonobese women, in whom 85 % were successful [36, 37]. And in women with BMI of 40 kg/m2 or higher, success was only 61 %. Furthermore, the investigators noted higher rates of uterine scar dehiscence, composite morbidity, and neonatal injury rates in the obese and morbidly obese women [36, 37]. In a study of extremely obese women, there were no differences in VBAC success rate between different obesity groups, although the success rates were low in all groups [20].
While these statistics might sway some to recommend repeat cesarean delivery over attempted VBAC, the surgical risks in overweight and obese women discussed earlier need to be considered. In a facility with adequate support, a trial of labor can certainly be attempted and should be considered. Again, adequate counseling during the prenatal period, not when the patient presents in labor, is ideal.
Special Considerations
As has been mentioned throughout this chapter, gestational diabetes mellitus (GDM) poses additional risk for the overweight and obese patient. Accurate diagnosis in this population is particularly important, given the implications for the fetus as well as for management of labor and delivery. In the recent Hyperglycemia and Adverse Pregnancy Outcome (HAPO) study, risk of birth weight over the 90th percentile was significantly increased when both GDM and obesity were present (OR 3.62) as compared to GDM alone (OR 2.19) or obesity alone (OR 1.73) [37, 38]. And although obesity alone is a risk factor for preeclampsia, GDM in addition to obesity was associated with an even greater risk of preeclampsia than either factor alone (OR 5.98) [37, 38]. Unfortunately, the ideal delivery management in patients with both GDM and obesity is not clear. Although there is no clear evidence to support the practice, some experts recommend individualizing care and considering cesarean delivery when estimated fetal weight is 4,000–4,500 g in GDM patients [38, 39]. Others have recommended earlier induction of labor in women with GDM [39, 40]. A recent systematic review, however, found that further research is necessary to inform timed delivery in patients with GDM [14, 40]. Furthermore, caution must be advised in patients with both GDM and obesity, as management in that population has not been as extensively studied.
Future Research
Clinical research on appropriate interventions in the overweight and obese population has not kept up with the gaps in our understanding. Several opportunities for research have already been mentioned. For example, a well-designed prospective study to characterize labor patterns in women of different weight classifications could inform guidelines and practice patterns. Such research would need to take into account the use of cervical ripening agents, amniotomy, and oxytocin. The use of intrauterine pressure catheters during such a study might also help inform the possible etiology of differences in labor curves. Because of the desire to avoid cesarean delivery in overweight and obese women, studies to examine the best policies and practices for induction of labor (or expectant management) in this population (with and without gestational diabetes) would also be extremely helpful to clinicians. For example, studies looking at characteristics of women with successful induction of labor can help clarify what factors should be considered when making such decisions. The management of patients with comorbid conditions, such as GDM and obesity, is another area that requires further research to determine recommended intrapartum management.
Another area where further research is needed is in the intraoperative and postoperative care of obese women who deliver by cesarean delivery. What is an adequate dose of antibiotics to adequately cover obese and super-obese women? Prospective studies should also look at prevention of thromboembolic disease, which is more likely in obese women and which remains one of the most significant causes of maternal mortality.
Throughout this chapter, we have recommended the implementation of shared decision making to help pregnant women with complicated decisions that may arise during the prenatal period. While engaging the expectant women might seem to be an easily attainable task, the art and science of shared decision making has not been extensively studied in the obstetrical patient. Patient and provider communication is critical in order to fully inform the patient of her choices and to integrate her values and preferences into her final decisions for care. Future studies looking at both perinatal outcomes and patient satisfaction with care would help inform how shared decision making can best be used during pregnancy.
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