Paul Lyons1
(1)
Department of Family Medicine, University of California, Riverside, Riverside, CA, USA
Key Points
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Background
Prenatal care is generally the most prolonged and sustained component of pregnancy care. Such care is often delivered by a single provider who will follow the course of the pregnancy with nearly as much interest as the pregnant patient. Although the prenatal period is often filled with anxiety, it is generally more relaxed and almost always less pressured than the labor and delivery setting. For these reasons, prenatal care provides patients with an opportunity to educate themselves and participate in the process of preparing for a new infant.
Prenatal care can best be thought of as a process rather than a specific event. For patients who received preconception counseling, it is a continuation of the threefold process of education, risk identification, and risk reduction/intervention. For those patients who did not receive preconception counseling, it should be the beginning of such a process. Many prenatal care providers also participate in the delivery of their patients. In this regard, prenatal care provides an opportunity to establish or enhance a relationship that stretches from preconception through prenatal management to delivery. Excellent prenatal care represents a partnership between the provider and the pregnant patient (and her family) with ample opportunity for discussion, questions, and answers and active participation by each person involved.
Prenatal care is a cornerstone of modern obstetric care and has accompanied a reduction in the historic risk associated with pregnancy. Maternal mortality in 1935 was 582 per 100,000 pregnancies. By 1993, that figure had decreased to 7.5 per 100,000. Over approximately the same period, infant mortality decreased from 47 per 1000 to 8 per 100,000. Although many factors unrelated to prenatal care have contributed to these reductions, prenatal care has directly contributed to improved outcomes in a variety of areas: (a) fetal organogenesis (folic acid supplementation, glycemic control in diabetes), (b) infectious disease detection/treatment (e.g., chlamydia, bacteriuria), (c) infectious disease transmission prevention (e.g., syphilis, HIV), and (d) fetal growth (e.g., glycemic control in gestational diabetes).
Figure 2.1 in Chap. 2 provides a schematic outline for the interrelated factors involved in pregnancy. Factors present during the preconception period were reviewed in the prior chapter. With the advent of conception, additional factors come into play. Pregnancy itself introduces a variety of new conditions that can impact the health of both the mother and the infant. Although less well described, a variety of paternal factors can also affect the course and outcome of pregnancy. Although not specifically addressed in this chapter, there are a number of physician- and system-related factors that can, likewise, impact pregnancy. The process of prenatal care is cyclical and repetitive. Each visit allows providers to review what has already happened and to determine what has developed in the interval since the last visit. Each visit will focus on patient education, determination of normal growth and development, and compilation of critical information in a variety of important domains.
Key Domains of Prenatal Information
The first step in any prenatal assessment is to confirm that the patient is, in fact, pregnant. Many patients will arrive for a first prenatal visit with a confirmed positive pregnancy test result. Other patients will arrive for their first “prenatal” visit with a variety of less clear presentations. They may have missed their period but not have been tested. They may have self-tested but not trust the results (either positive or negative). Regardless of the nature of the uncertainty, all patients with uncertain pregnancy status should have their status confirmed via urine or serum human chorionic gonadotropin (hCG) testing. Following confirmation of pregnancy, all patients should have the opportunity to consider what the most appropriate next step should be. When uncertain regarding the desirability of a confirmed pregnancy, providers should be cautious in their choice of language. In particular, providers should avoid the use of language that implies a specific outcome such as “Congratulations, you’re pregnant!” or “We will need to get you started with prenatal care soon.” The use of open-ended questions such as “The test confirms that you are pregnant. What do you think you would like to do at this point?” will allow patients to more easily express their thoughts concerning subsequent management.
Initial evaluation during prenatal care is similar to the evaluation for preconception counseling. It is designed to focus on the patient’s baseline condition and any development in the time frame from the last menstrual period (LMP) through the first prenatal visit. (This is a time period during which patients may not recognize that they are pregnant and may include significant exposures to infectious or toxic agents.) At intake prenatal screening provides important information in six key domains:
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As discussed in the previous chapter, these domains of information can form the basis for patient education and intervention throughout the course of pregnancy (and beyond).
Following the initial prenatal screen, subsequent visits focus on interval developments and review of previously identified issues. It is often helpful to develop a prenatal problem list to organize ongoing issues under management. Such a list could include the problem, the date identified, interventions, if any, and the date resolved, if applicable. Follow-up prenatal care will focus on three key domains: (a) normal growth and development, (b) medical and/or obstetrical complications of pregnancy, and (c) onset of labor.
Frequency of Prenatal Visits
The frequency of visits during prenatal care is dependent on the complexity of the care being provided. For those patients with complex presentations, individualized decisions must be made concerning the frequency of prenatal visits. For patients with uncomplicated pregnancies, the currently recommended frequency for visits is as follows:
· First prenatal visit: in the first trimester
· Follow-up visits: every 4 weeks until 30 weeks gestation, then
o every 2 weeks until 36 weeks gestation, then
o every week until delivery at term, or
o twice weekly from 40 weeks for assessment of
o fetal well-being (see Chap. 18).
The First Prenatal Visit (See Table 3.1)
Table 3.1
First prenatal visit
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Last menstrual period (LMP) |
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Duration, abnormalities, fertility treatment, contraceptive use, and prior pregnancies |
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Prior obstetrical history: all prior pregnancies including elective and spontaneous abortions |
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All pregnancies: date, outcome, weeks of gestation |
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Deliveries: gender and weight of infant, duration of labor, delivery method, anesthesia, and complications, if any |
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General medical history: including all pertinent medical conditions but focused on |
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Anesthesia history |
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Medications |
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Medication allergies |
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Toxic exposures (including tobacco, alcohol, and illicit drugs) |
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History since LMP: events or exposures during early organogenesis |
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Drugs, medications, and radiation |
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Infectious diseases (cytomegalovirus, toxoplasmosis, tuberculosis) |
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Possible pregnancy-related symptoms (bleeding or discharge per vagina, abdominal pain, headache, visual complaints, emesis) |
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Family history: comprehensive but with an emphasis on |
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Fetal deaths or abnormalities |
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Multiple gestations |
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Genetic history (cystic fibrosis, Down syndrome, thalassemia) |
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Chronic medical conditions with strong familial link (e.g., hypertension, diabetes mellitus, renal disease, substance abuse) |
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Safety |
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Abuse, including sexual abuse |
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Domestic violence |
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Seat belt use |
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Environmental risks including work-related hazards |
The first prenatal visit lays the groundwork for all subsequent visits and therefore includes the most comprehensive history, physical examination, and diagnostic testing. For patients who have had one or more preconception counseling visits, much of the information can be obtained from the records of those visits. Information subject to change will need to be updated and a brief review of all material should be performed to ensure accuracy and completeness. Many offices utilize one of the many standardized obstetrical health history and prenatal flow sheet forms that exist in both paper and electronic form. In addition to providing a standardized method for recording necessary information, the flow sheets can serve as a prompt for providers throughout the course of pregnancy.
History
Menstrual History. The preconception history begins with the LMP. Information should include the date of the first day of bleeding and the duration. The certainty of this date is of considerable importance as this forms the first basis for predicting the estimated date of delivery (EDD, or confinement in some older references). Depending on a variety of factors, including regularity of menses, duration since LMP, and whether patients track menses regularly, patient recall of their LMP may be of variable reliability. Some notation of the patient’s subjective “certainty” concerning the date should be recorded. First-trimester bleeding is a relatively common complaint and may mimic menstruation. For this reason, patients should be questioned concerning the timing and quantity of bleeding as well. A “period” that is abnormally light or heavy or fell out of the normal cycle may represent an event of pregnancy rather than the true LMP.
Prior Obstetrical History. Prior obstetrical history can significantly impact the current pregnancy. For this reason all prior pregnancies should be summarized in the prenatal record. For all prior pregnancies, documentation should include the date of the pregnancy, the outcome (full-term delivery, preterm delivery, spontaneous abortion, elective abortion) and the weeks of gestation completed. For those pregnancies that resulted in live delivery, additional key information would include date of delivery, gender and weight of the infant, duration of labor, delivery method and anesthesia use, or complications, if any.
This information can be summarized in short-hand form as gravida/para figures. This notation takes the form of GxPxxxx. G(ravida) represents the total number of pregnancies regardless of outcome. P(ara) represents, in order from left to right, full-term deliveries, preterm deliveries, abortions (elective or spontaneous), and living children. Although it does not include all of the details of each pregnancy, this short-hand form provides a quick and convenient summary that is especially useful in oral or written presentations.
General Medical History. All pregnancies occur within the context of the patient’s baseline health status. Many medical conditions may impact the course of pregnancy. At the same time, pregnancy may have a significant effect on a variety of pre-existing medical conditions. It should also be recognized that delivery is a surgical procedure in many instances with approximately one-fourth of all deliveries occurring via cesarean section. For this reason, a comprehensive review of the patient’s general medical history should be recorded. Special emphasis should be placed on chronic medical conditions, prior surgical and anesthesia history, medications, medication allergies, and substance use including tobacco, alcohol, and illicit drug use.
History Since LMP. Particular attention should be paid to medical events between the LMP and the first prenatal period. This represents the critical period of organogenesis during which a variety of medical conditions and exposures may have significant impact on the developing fetus. In particular, note should be made concerning management and/or control of chronic medical conditions that may impact fetal development such as hypertension and diabetes mellitus. Exposure to a variety of toxic and infectious agents is also important during this time period. Note should be made of exposure to drugs, medications, live vaccine preparations, or radiation. Known or suspected exposure to infectious agents should also be documented including sexually transmitted disease, cytomegalovirus, toxoplasmosis, tuberculosis, HIV, rubella, or varicella.
In addition to exposures, this period of early pregnancy is also marked by a variety of potential complications of pregnancy such as abnormal implantation or hyperemesis gravidarum. Patients should be screened for possible pregnancy-related symptoms such as bleeding or abnormal discharge per vagina, abdominal pain, headache, visual complaints, and severe nausea or vomiting.
Family History. A number of familial conditions and events are of potential consequence in pregnancy. A family history should be obtained with an emphasis on fetal deaths or abnormalities, multiple gestations, gestational diabetes, large- or small-for-gestational-age infants, significant genetic history (e.g., cystic fibrosis, Down syndrome, thalassemia), and chronic medical conditions with a strong familial link such as hypertension, diabetes, renal disease, and substance abuse.
Physical Examination
All patients should receive a comprehensive physical examination. The purpose of the examination is threefold:
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A variety of physical changes can be noted during pregnancy. Although underlying medical conditions must be excluded, these findings generally represent benign changes and should be noted primarily for reference in case of change. Such findings include split S1 and/or a systolic ejection murmur on cardiac examination, mild thyroid enlargement, skin changes including malar rash and striae gravidarum, and accentuated lordosis noted on musculoskeletal examination.
Evaluation of uterine size is helpful in confirming the gestational age. At 6 weeks’ gestation, the uterus has enlarged beyond its prepregnant dimensions and is described as the size of an orange. By 8–10 weeks, the uterus is described as grapefruit sized. At 10–12 weeks, the uterus is palpable on abdominal examination at the symphysis pubis. Once the uterus is palpable from the abdomen, measurement is made of the fundal height. This measurement represents the distance from the symphysis pubis to the top of the uterine fundus. By 20 weeks’ gestation, the uterine fundus should normally be found at the level of the umbilicus. From 20 to 34 weeks’ gestation, measurement of the fundal height (in cm) should be equivalent to the gestational age (in weeks). For example, at 28 weeks’ gestation, the fundal height should be approximately 28 cm from symphysis to the top of the uterine fundus (±2 cm). Any significant deviation from these expected measurements should prompt the provider to reassess the gestational age and/or fetal development.
Assessment of the bony pelvic configuration (clinical pelvimetry) is often performed early in pregnancy to determine potential structural impediments to successful delivery. Abnormal findings do not rule out the possibility of a trial of labor and successful vaginal delivery but added caution may be warranted at the time of delivery. Notation should be made of the diagonal conjugate (distance from symphysis pubis to sacral promontory), ischial spines (blunt, prominent) sacrum (concave, straight), coccyx (fixed, mobile), and the pubic arch (normal, wide, narrow).
Laboratory and Diagnostic Testing
As previously noted, all patients for whom pregnancy status is uncertain should have a confirmatory pregnancy test. This may take the form of either a urine or serum test for hCG. The urine hCG test is generally positive beginning at the time of the first missed period (approximately 4 weeks gestation). The serum test is generally positive at the time of implantation.
For all prenatal patients, routine obstetrical laboratory screening should include complete blood count with platelets, blood type (ABO and Rh), rapid plasma reagin, rubella titer, hepatitis B surface antigen (to detect active disease), HIV antibody, Papanicolaou smear (if not performed within the preceding 3 months), gonorrhea and chlamydia screen, and routine urine analysis with culture.
Selected patients may also benefit from screening for the following conditions: sickle cell disease (via routine screen or hemoglobin electrophoresis), Tay–Sachs, toxoplasmosis, cytomegalovirus, elevated serum lead, elevated glucose, substance use, and/or herpes simplex virus.
These screening tests are recommended at the first prenatal visit, which should routinely occur in the first trimester. For those patients who present for a first prenatal visit later in pregnancy, laboratory and diagnostic testing should include those tests just mentioned as well as all tests appropriate to their estimated gestational age at the time of presentation. These additional tests are described later.
Estimating Gestational Age
At the conclusion of the first prenatal visit, a clinical assessment of gestational age and estimated date of delivery should be established. If the available information is incomplete or contradictory, a tentative date may be assigned with arrangements for acquisition of more definitive data.
The available data that may contribute to establishment of the gestational age includes the following:
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Laboratory Testing
Levels of hCG obtained via quantitative testing are not considered accurate for dating purposes as significant variability is noted at any given gestational age.
As a general rule, the first gestational age/EDD assigned should remain unchanged throughout the pregnancy unless significant doubt exists concerning the data used to establish that date. Caution should be exercised when “correcting” an EDD based on later data.
Treatment and Follow-Up
All patients not already taking prenatal vitamins should be given a prescription and encouraged to immediately begin taking one vitamin per day. In addition, iron supplementation should be considered for those patients with documented anemia.
At the first prenatal visit, patients should be given an overview of the course of prenatal care, a general caution concerning warning symptoms that should prompt early follow-up, and arrangements should be made for an appropriate follow-up visit. Patients should be given the opportunity to ask questions and to clarify any areas of uncertainty. It may be helpful to suggest that patients keep a list of written questions between visits to help ensure that all important concerns are addressed at each visit.
Follow-Up Prenatal Visits
Follow-up visits are designed to meet four purposes: to track the progress of the pregnancy; early identification of complications, if any; completion of testing/evaluation at specific gestational-age milestones; and patient education/anticipatory guidance.
Follow-up visits provide the opportunity to elicit patient questions and concerns and to provide education and counseling. Topics for review include nutritional status, activity and exercise in pregnancy, and symptoms consistent with preterm labor. Plans for delivery, such as when to contact the provider and when to go to the hospital, should be addressed. Also discussed should be issues related to delivery and the postpartum period, including use of anesthesia, breastfeeding, circumcision, and the duration of the postpartum stay.
Follow-up intervals noted here are for uncomplicated pregnancies. Follow-up must be arranged as indicated should abnormalities present at any point.
Interval History and Physical Exam
The interval history should focus primarily on events and developments in the time period from the last visit to the current visit. Review of unresolved or ongoing concerns should also occur. Aspects of the history that should be addressed at every visit would include fetal movement (presence or absence and quantity), uterine contractions, pelvic pain or pressure, abdominal or back pain, and discharge or bleeding per vagina.
The physical examination contributes to assessment of fetal development and may also provide clues to the detection of pregnancy-related complications. The core elements of the physical examination include blood pressure, notation of edema, and weight. Assessments of fetal development include measurement of fundal height and documentation of the fetal heart rate.
Appropriate weight gain in pregnancy is a very common concern for pregnant patients. In population studies, optimal outcomes have been associated with maternal weight gain of 20–25 lb during pregnancy. Current recommendations for weight gain during pregnancy suggest 25–35 lb for a woman of average weight at the onset of pregnancy. Decreased weight gain can be associated with inadequate nutritional intake, inaccurate dating, intrauterine growth retardation, oligohydramnios, and fetal demise. Increased weight gain can be associated with excessive caloric intake, inaccurate dating, macrosomia, multiple gestation, and polyhydramnios. Abnormal weight gain should prompt review of the prenatal course, eating patterns, and fetal well-being surveillance.
Interval Laboratory and Diagnostic Studies
Each pregnancy will require individualization of appropriate interval laboratory and diagnostic studies. For most pregnancies, however, a variety of interval studies should be considered. These include the following:
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