Prenatal Care

Prenatal Screening

One of the first tasks is to establish that the woman is indeed pregnant. Through the ready availability of home pregnancy tests and recognition of a missed menstrual period, many women have already self-diagnosed a pregnancy. Pregnancy tests (urine or blood) are so sensitive that they are positive 6 to 8 days after fertilization, Well before a missed menstrual period.

History

Medical History Prenatal care usually begins with a complete medical history taken at the first visit, including use of medications (both prescription and nonprescription), vitamins, and any alternative/complementary medicines (e.g., herbs).

The medical interview should also reveal any history of hypertension, diabetes, or other significant medical problem that could affect the pregnancy. Such women will require special surveillance during their pregnancy. A history of exposure to infectious diseases such as tuberculosis, toxoplasmosis, or rubella should be noted.

Pregnancy History One of the most important predictors of success in a pregnancy and delivery is a good outcome in a previous pregnancy. The past pregnancy history should be carefully reviewed, with special attention directed toward the previous method of delivery and any obstetric or medical problems that developed. Women who previously experienced preterm labor, cervical incompetence, gestational diabetes, hypertension, or postpartum hemorrhage are at risk for a recurrence of these problems.

 

Follow-up History On subsequent visits, smoking, diet, medication use, and health habits are again reviewed, in addition to an ongoing assessment of the woman’s social situation. Women should be questioned about the presence or absence of symptoms such as nausea, vomiting, headache, abdominal pain, and vaginal bleeding or discharge. Her attitude toward birth and breast-feeding should be explored as well.

Physical Examination

First Visit The first prenatal visit should include a thorough physical examination, with special attention directed toward the size of the uterus and the shape of the pelvis, along with establishing the patient’s baseline blood pressure and weight. A bimanual examination of the uterus can help determine the gestational age, The clinician should also attempt to listen to the fetal heartbeat, which can be heard with a Doppler ultrasound device at 10 to 12 weeks and with a fetoscope at 18 to 20 weeks.

Subsequent Visits On subsequent visits, the physical examination usually is limited to checking weight and blood pressure and looking for peripheral edema. A sustained blood pressure of greater than 140 mmHg systolic or 90 mmHg diastolic suggests a hypertensive disorder of pregnancy, which will require intensive surveillance and possible early induction. Preeclampsia is hypertension associated with peripheral edema and protein in the urine.

After the first trimester (weeks 0 to 13), uterine growth is measured from the pubic symphysis to the top of the fundus. At 20 weeks the uterus is palpated at the level of the umbilicus; expected growth from 21 weeks on is about 1 cm/wk. A uterus that is greater than 2 cm larger than anticipated, particularly over several visits, means that the pregnancy is farther along than expected, the woman is carrying twins, or an obstetric problem such as polyhydramnios or macrosomia is present. A smaller than expected uterus (> 2 cm less than expected) can mean that the pregnancy is less advanced than presumed or an obstetric problem such as oligohydramnios or intrauterine growth retardation is present. The fetal status is further assessed by verifying a fetal heartbeat and, in the third trimester, by ascertaining the baby’s position of presentation in the uterus, that is, determining where the head is in relation to the cervix. This is important because a breech or transverse lie has a profound impact on the method of delivery, often mandating a cesarean section. However, if such a malpresentation is discovered before the last 2 to 4 weeks of pregnancy, it is often possible to turn the baby (version) to a vertex (head down) position, giving the woman a significantly improved chance for a vaginal delivery.

Laboratory Screening

Blood Type Several laboratory tests are routinely drawn during prenatal care. At the initiation of prenatal care, a pregnant woman’s’ blood type is determined to see if her red blood cells carry the A or B antigen and/or the D (formerly Rh) antigen. Only about 15 percent of people are negative for the D antigen. When a D-negative woman has a D-positive fetus (inherited from the father), the woman may develop an antibody to the infant’s D antigen that crosses the placenta into the fetal circulation, destroying the fetal red blood cells leading to anemia, hyperbilirubinemia, or fetal hydrops. The incidence of this problem, known as erythroblastosis fetalis, has dropped dramatically in the past 30 years for two reasons. First, women are not having as many babies, and the incidence of isoimmunization increases with each subsequent pregnancy in a D-negative woman. Secondly, the availability of anti-D gammaglobulin, known as RhoGAM, has been one of the major obstetric achievements of the past 30 years. RhoGAM is given anytime there is a risk of fetomaternal bleeding, such as after an amniocentesis, and is given routinely at 28 weeks.

Ater delivery, the baby’s blood type is determined and if D-positive, the mother will be given another dose of RhoGAM within 72 h of birth. These practices are effective and safe, so these protocols are highly recommended.

Hemoglobin Hemoglobin or hematocrit is also determined early in pregnancy because evidence suggests that significant anemia can be associated with poor birth outcomes. Cutoff values for anemia in pregnancy whose hemoglobin or hematocrit fall below these levels should be treated with iron a follow-up test should be performed later in pregnancy to document a response to treatment. Unfortunately, the normal drop in hematocrit that occurs during pregnancy, due to expansion of the plasma volume, is frequently misinterpreted as iron deficiency. There is no evidence that iron supplementation is beneficial unless there is true iron-deficiency anemia. In fact, some evidence indicates that iron supplementation can even worsen outcomes, possibly by increasing the viscosity of the maternal blood. Women who develop significant anemia and are at risk for hemoglobinopathies such as sickle cell disease and certain thalassemias (women with a family history or who are of African, Mediterranean, Middle Eastern, Southeast Asian, or Latin American descent) should have hemoglobin electrophoresis.

Rubella Rubella immunity is determined by assessing for antibodies to rubella, although ideally this is done before pregnancy when there is the opportunity to vaccinate nonimmune women. Maternal rubella infection in early pregnancy can lead to miscarriage, stillbirth, and the devastating effects of congenital rubella syndrome. The non-immune pregnant woman should be advised to stay away from individuals with known outbreaks of rubella and should be vaccinated in the Postpartum period.

Hepatitis B Hepatitis B surface antigen is part of initial screening. A positive result indicates active (acute or chronic) hepatitis B infection, and babies born to these mothers need hepatitis B immunoglobulin and vaccination at birth.

Genitourinary Infection Gonorrhea and chlamydia infections are often asymptomatic infections associated with poor outcomes such as premature delivery and neonatal infection, so pregnant women are screened for these infections. Cultures are obtained from a swab of the endocervix.

Asymptomatic bacteriuria in pregnancy is associated with an increased risk of maternal pyelonephritis, preterm delivery, and low birth weight, but recognition and treatment can reduce the incidence of these problems significantly. Screening with a urine culture is recommended for all pregnant women at 12 to 16 weeks of gestation.

Bacterial vaginosis, an overgrowth of predominantly anaerobic bacteria, has been associated with preterm birth.32 Randomized trials involving women at high risk for preterm delivery (history of preterm delivery, a low prepregnant weight of < 50 kg, or both) showed that treatment of bacterial vaginosis with metronidazole either alone or with erythromycin substantially reduced the rate of preterm birth. Hence, women at high risk for preterm delivery who have a positive screen or symptoms of bacterial vaginosis should be treated with metronidazole administered orally (vaginal treatment does not appear to be as effective as oral). There is no evidence at this time that this strategy should be adopted for women at low risk for preterm delivery.

It is now routine to screen pregnant women at 34 to 37 weeks with a rectovaginal culture (and not a cervical culture) to identify those who are carriers of group B streptococcus (GBS). Neonatal GBS infection can be devastating and is usually acquired by the baby during childbirth. In the United States, GBS sepsis occurs in 1.8/1000 live births with a case-fatality rate of 5 to 20 percent, leading to about 310 newborn deaths per year. Women who are identified as GBS carriers are offered treatment with antibiotics during labor, which can significantly lower the risk of transmission. An alternative strategy is to omit the prenatal screening but treat with antibiotics during labor any women who develop fever, have ruptured membranes more than 18 h, deliver before 37 weeks’ gestation, had GBS bacteriuria in the pregnancy, or had a previous infant with significant GBS disease.

Repeat Testing Other laboratory tests performed in the third trimester include repeat testing for syphilis, gonorrhea, chlamydia, HIV, and hepatitis in women with behaviors that place them at increased risk for acquiring these infections.

Prenatal Diagnosis Of Congenital Malformations

It is the hope of every pregnant woman and her family that the expected baby is born healthy. However, congenital malformations occur in about 3 percent of newborns. Although most of these malformations are minor, some are life-threatening and congenital anomalies are now the leading cause of infant mortality in the United States. Infants with congenital malformations who survive may require lifelong special care, which has a tremendous impact on families. Many pregnant women want the opportunity to minimize the chance of this happening to their families and choose prenatal diagnosis, which is now routinely offered in some form to all pregnant women. Assessment of genetic risk should begin even before a women is pregnant, with a careful history of familial genetic defects or any risks related to ethnicity, such as sickle cell disease in people of African descent or Tay-Sachs disease in those of Jewish heritage. Other defects can be detected through antenatal screening.

It is the standard of care to offer prenatal diagnosis to every pregnant woman, but each woman should be thoroughly counseled as to the limitations of these tests and that there is always the risk of a false-positive test, which can lead to tremendous anxiety along with a cascade of further testing. Counseling by the health care provider should be accurate, thorough, and nonbiased, with each couple’s individual preferences respected. Referal to genetic counselors is often useful when women and their families are faced with these decisions.

Women may wish for testing even if they know that they will not choose to terminate the pregnancy. Because there is no evidence that early detection of congenital anomalies improves outcome, the rationale for prenatal testing in such families is questionable. Some parents, however, may feel that the opportunity to prepare for the arrival of a child with malformations is important to them. In some situations, knowledge about a physical deformity before birth, such as a cardiac or abdominal defect, will allow for delivery at an institution with skilled personnel and appropriate facilities to maximize the chance for survival. The possibility of organ donation, in the case of a child with lethal anomalies (e.g., anencephaly) may be another option for a family.

Neural Tube Defects Screening for neural tube defects such as spina bifida, anencephaly, and encephalocele is offered during the early second trimester of care. These defects occur in 4/10,000 live births. A test measuring the maternal serum a-fetoprotein (MSAFP) between 15 and 19 weeks’ gestation is used to predict neural tube defects. About 1 to 5 percent of women will have an elevated (abnormal) MSAFP, but 90 to 95 percent of these women actually have babies without a neural tube defect, and the falsely elevated level is due to underestimated gestational age, multiple gestation, or other anomalies. An ultrasound should be performed to assess for any of these causes. Amniocentesis should be offered to those women still without an explanation for the elevated MSAFP.

Ultrasound

Ultrasonography has had a profound effect on prenatal care, and it is accepted widely and even expected by many pregnant women. It is most commonly used to estimate the due date. A scan in the first trimester predicts the due date within a week of reliability a scan in the second trimester can predict the estimated date of confinement within 2 weeks of reliability. Ultrasonography is also used to detect multiple gestations or malformations, assess fetal growth, evaluate vaginal bleeding, and provide reassurance of fetal health in late pregnancy.

Although there is no doubt that ultrasound is useful when clinically indicated, routine ultrasound of all pregnancies is not recommended. The largest clinical trial to date studied 15,151 low-risk pregnant women and reported that routine ultrasound (ultrasound performed without a clinical indication) does not affect maternal or fetal outcomes. The National Institutes of Health, the American College of Obstetricians and Gynecologists, and the Preventive Services Task Force all have taken the position that ultrasound should be used only when there is a specific medical indication. Indications for ultrasonography during pregnancy.

Despite these recommendations, many pregnant women expect and desire an ultrasound examination. Due to cost concerns and evidence that routine ultrasound does not improve outcomes, the use of this technology does not appear warranted, but it remains a popular procedure among pregnant women and clinicians alike.

Management Strategies

Promoting Good Health In Pregnancy

A woman’s body undergoes marked physiologic changes during pregnancy. Her blood volume increases by almost 50 percent, her endocrine system undergoes dramatic alterations, and her organs adjust to the profound anatomic and metabolic changes of pregnancy. In addition to these remarkable physiologic changes, most women are committed to taking good care of themselves during pregnancy.

Nutrition And Weight Gain It is presently recommended that an average-sized woman should gain 25 to 35 lb during pregnancy. Underweight women and adolescents (who may still be growing themselves) require a 28- to 40-lb weight gain to reduce their risk of having a low birth weight baby. Women who are overweight at the onset of pregnancy, or who gain excessively during the pregnancy, have an increased incidence of hypertension and diabetes along with a tendency to produce large babies that can lead to difficult labors and operative delivery. Data are insufficient to demonstrate exactly how much weight obese women should gain. Because some have found an increased risk of intrauterine growth retardation in obese women with little weight gain, it is generally recommended that obese women gain at least 15 lb. It is often obsetVed anecdotally that some obese women have healthy babies with lower gains.

Vitamin And Mineral Supplements Most women are encouraged to take a prenatal vitamin during pregnancy. These are multivitamin preparations containing iron (usually 60 to 90 mg); zinc; copper; calcium (usually 250 mg); vitamins B, C, and D; and folate (usually 1 mg). If vitamin A is included, l3-carotene is preferred over retinol to reduce the risk of toxicity. Because calcium and magnesium may interfere with iron absorption, upper limits of 250 mg and 25 mg per dose, respectively, are recommended as part of the vitamin supplement. Because many women experience nausea and vomiting during the first trimester, and vitamins may worsen these symptoms, supplemental minerals and vitamins can be started in the second trimester.

Folk Acid. Folic acid reduces the risk of neural tube defects (spina bifida, anencephaly, or meningomyelocele), and dietary supplementation with 0.4 to 1 mg daily should ideally begin before conception and continue through the first 3 months of pregnancy.

Iron.It is recommended that all pregnant women supplement their diet with 30 mg elemental iron daily during the second and third trimesters. There is no evidence that further supplementation with iron is beneficial to the mother or the baby, except in those women with true iron-deficiency anemia. In fact, concern has been raised that excess iron may lead to zinc depletion, which is associated with intrauterine growth retardation. In addition, iron supplementation can cause stomach upset, nausea, and constipation, although sustained-release preparations can lower the incidence of these side effects. The best food sources for iron include meats, chicken, fish, legumes, leafy vegetables, and whole grain or enriched breads and cereals. Tea and coffee can limit the absorption of iron and should be avoided at meals at which good sources of iron are eaten.

If a woman is experiencing iron-related side effects (as noted above) from a standard prenatal vitamin, a preparation with 30 mg iron should be substituted. This can be accomplished by using a nonprescription prenatal vitamin or two children’s chewable vitamins with iron.

Vitamin A. Excess ingestion of fat-soluble vitamins should be avoided, particularly vitamin A, which can cause birth defects at dosages just three to four times higher than the recommended daily allowance. Use of l3-carotene, the precursor of vitamin A found in fruits and vegetables, has not been shown to produce vitamin A toxicity. Supplementation with 5000 IU vitamin A perday should be considered the maximum intake before and during pregnancy. This is well below the minimum human teratogenic dose, which is probably at least 25,000 to 50,000 IV daily. Prenatal multivitamins in common use contain 5000 IU or less of vitamin A, but vitamin tablets containing 25,000 IU or more of vitamin A are available as nonprescription preparations, so care should be exercised.

Other Minerals. It is generally recommended that women ingest 1200 mg calcium daily during pregnancy; many women’s diets do not provide this amount. These and other supplements are currently being studied, but at this time there is no evidence that the addition of multivitamins, zinc, magnesium, calcium, or even fish oil is of any benefit to the mother or her baby. An exception can be made for those women who truly have a marginal nutritional status imposed by social or economic limitations.

Breast-Feeding

No discussion on nutrition is complete without mentioning breast-feeding, the optimal nutritional choice for the baby. Breast milk is rich in nutrients, is easily digested, is readily available and inexpensive, and promotes the mother-baby relationship. Breast milk furnishes the necessary immunologic protection while the infant’s immune system is maturing. Breast milk contains antibodies against common bacteria, viruses, and other pathogens, as well as providing anti-inflammatory agents and immunomodulating factors. It also decreases the risk for immunologic disorders such as atopy and allergies. The evidence in support of breast-feeding is so overwhelming that entire texts have been devoted to detailing the art and science of breast-feeding.

Women need to maintain healthy lifestyle habits while breast-feeding because drugs, tobacco toxins, and alcohol will pass into the breast milk. Breast-feeding women should maintain an adequate intake of calcium, especially because bone density decreases during lactation.

Common Nonpregnancy-Related Problems

some symptoms that are common and often occur during pregnancy. These include colds, allergies, headaches, urinary tract infections, and vaginitis.

Upper Respiratory Infections Many popular remedies have been proposed for colds, from chicken soup to vitamin C. There is still no cure for the common cold, but some drugs for symptomatic relief that can be used in pregnancy. Pharmacologic treatments for allergies and headaches are listed as well. Urinary tract infections usually require antibiotic treatment for eradication.

Vaginitis Vaginal infections also occur in pregnancy. Yeast infections are common and can cause intense itching. There can be a white vaginal discharge, although it can be difficult to differentiate between this and the normal increase in discharge that occurs during pregnancy. Azole antifungals applied vaginally, such as miconazole are usually the therapy of choice and can be used in the first trimester. Oral azole antifungal agents are contraindicated in pregnancy.

Bacterial vaginosis can cause a “fishy” odor, a white, yellow, green, or gray discharge, and itching caused by an overgrowth of anaerobic bacteria in the vagina. It is thought to be associated with miscarriage, premature rupture of membranes, and preterm delivery.Oral or topical clindamycin or metronidazole can reduce the symptoms as well as the associated risks. The use of metronidazole in early pregnancy remains controversial. Although some studies report it is safe to use even in the first trimester, it is probably prudent to avoid its use until the second alld third trimester. Clindamycin is a safe and effective alternative.

Trichomonas is a protozoa that can cause itching and discharge, although women are often asymptomatic. It is unclear whether trichomollas itself causes adverse pregnancy outcomes. As a sexually transmitted disease, it is often associated with other sexually transmitted diseases that are of known significance during pregnancy, so thorough evaluation is warranted. The only known effective treatment for trichomonas is metronidazole. Clotrimazole is often suggested as an alternative in the first trimester, even though it is only effective in a minority of cases.

Nonpharacologic Methods

Many women express a desire to avoid pharmacologic pain relief, and this preference should be supported, within reason. Prenatal care should include education to familiarize women with the choices available to reduce labor pain. Although the overall effects of prenatal classes cannot be generalized because of variation in the quality of the instruction and the attitudes conveyed, the existing evidence does suggest that they are associated with less use of analgesic medication during labor.

Touch (e.g., stroking, massage) and movement (ambulation, position change, etc.) can be therapeutic during labor and are widely practiced in many cultures. Although the effectiveness of these measures has not been extensively studied, most experienced caregivers have found that counterpressure on the low back applied by a support person can alleviate back pain in some laboring women. Experience also shows that laboring women experience less pain in some positions than in others and can be trusted to select the positions that they find the most comfortable. Position changes can enhance the progress of labor as well; movement by the laboring woman should not be restricted.

Observational evidence suggests that the use of heat (hot -water bottles, hot towels, baths, and showers) and cold (ice packs and cool towels) can alter the perception of pain. These measures can be applied to the face, belly, perineum, and low back.

Focused concentration, visualization, relaxation techniques, music, and hypnosis have all been touted as being helpful in managing pain. Data on their effectiveness are limited, but there are no known adverse outcomes from these approaches.

Transcutaneous electrical nerve stimulation is a noninvasive method of pain control that transmits low-voltage electrical current to the skin, resulting in a “buzzing” sensation. The results of a few clinical trials were inconclusive, and the use of such a device is not widespread.

Pharmacologic Methods

Opiates, alcohol, and various other concoctions and potions have been used since ancient times. The challenge is to find a method that is effective in relieving pain while not compromising the health of the mother or the baby.

Narcotics Narcotics are widely used and reasonably effective. Unwanted maternal side effects include hypotension, nausea, vomiting, dizziness, and delayed stomach emptying. Of even more concern is the respiratory depression and decreased alertness that can be observed in the newborn. This can be minimized by judicious dosing and avoiding use within an hour or two of delivery. Respiratory depression at birth due to maternal narcotic use can be reversed with intramuscular naloxone given to the newborn.

Regional Anesthesia Regional anesthesia is widely used in labor. Epidural anesthesia is the most popular form of regional anesthesia and is effective in providing pain relief. However, a number of adverse outcomes are associated with its use including increased need for oxytocin, prolonged labor, increased rates of instrumental deliveries, and possibly increased rates of cesarean section. In a recent randomized trial of epidural versus patient-controlled meperidine analgesia during labor, however, there was no difference between groups in rates of cesarean section. Epidurals frequently cause maternal temperature elevation that is difficult to distinguish from maternal infection and can lead to unnecessary testing and treatments in the newborn.

Spinal (i.e., intrathecal) analgesia is gaining in popularity because it usually provides effective analgesia with an opioid without needing to use a local anesthetic. Unfortunately, it commonly has the side effects of nausea, pruritus, and headache. Spinal anesthesia can be used for operative deliveries because it has a rapid onset of action and is relatively easy to administer.

Paracervical block provides adequate analgesia but has fallen out of favor due to reports of fetal bradycardia, acidosis, and fetal death associated with its use. A pudendal nerve block and local perineal anesthesia are both effective methods of pain management in the second stage of labor.

Inhalation anesthesia (nitrous oxide) used to be a popular method of pain relief but is no longer used due to side effects of nausea and vomiting as well as concern for the medical staff repeatedly exposed to such gases.

Position in Labor and Delivery

When allowed to choose any position without interference or instruction, most women frequently change position in labor, using an average of 7.5 different positions’ The squatting position may offer an advantage because it enlarges the pelvic outlet by about 25 percent and makes use of gravity. Some studies have found that labor is shorter with a vertical position (sitting, standing, squatting, or kneeling). Sidelying, or the lateral Sims’ position, allows the clinician good visualization and results in a reduced need for episiotomy. There is no evidence that the supine position confers any advantage to the laboring woman, and because the uterus may compress the woman’s aorta and vena cava in this position, hypotension and fetal compromise may occur.

Women should be allowed to labor freely in the positions they choose, with birth attendants displaying flexibility and competence using different positions for delivery.

Continuous Electronic Fetal Monitoring

Electronic fetal monitoring is a classic example of applying a technology originally intended for high-risk patients to the general population before it is of proven benefit. When adequate studies were finally conducted, it was found that routine use of continuous electronic fetal monitoring compared to intermittent auscultation does not improve fetal outcomes but does increase the incidence of cesarean sections. This technology may be helpful when used to monitor suspected fetal distress; in this situation, a fetal scalp capillary sample for blood pH can be used to confirm fetal compromise. A scalp pH value of less than 7.20 requires intervention (usually cesarean section), a pH of 7.20 to 7.25 requires repeat evaluation within 20 mins, and a pH of above 7.25 is reassuring. Internal scalp electrodes for monitoring the fetal heart rate should be considered when heart tones cannot be adequately detected with an external Doppler device or to evaluate beat-to beat variability of the fetal heart rate.

Episiotomy

An episiotomy, or incision of the perineum just before delivering the head, is still performed by many clinicians who believe that it prevents damage to the perineum, anal sphincter, and rectum; is easier to repair than a tear; and prevents pelvic relaxation or urinary incontinence in later years. Studies, however, find either no difference in the rates of severe perineall acerations or more severe lacerations among women who received episiotomies. No data support the contention that episiotomy prevents pelvic relaxation, and the only randomized trial found no differences in urinary incontinence or dyspareunia. Episiotomy should be limited to situations where it is needed to expedite delivery in cases of fetal distress.

Amniotomy

Amniotomy, or deliberate rupture of the fetal membranes, is a procedure performed for the purpose of inducing or augmenting labor, evaluating amniotic fluid for the presence of meconium, for placing a fetal scalp electrode, or obtaining fetal scalp blood to assess the baby’s pH status. Amniotomy can shorten labor by 1 or 2 h, but it can also occasionally result in increase uterine forces, cord prolapse, and increase potential for maternal or fetal infection.

Other Choices in Labor

Whether a woman delivers in a hospital, birth center, or at home, she should be given choices in labor. Although hospitals need policies for efficient functioning, they must allow flexibility toward individuals, especially because many rules and routines are of no proven benefit and may actually do more harm than good. For example, it is important to remember that the newborn baby belongs to the parents, not to the hospital, and policies that separate the baby from the mother should be abandoned. Women and their families should be treated with dignity, afforded privacy, and approached as individuals. Choice regarding who is in the room, what food and drink is consumed, and what clothing is worn by the laboring woman are small efforts that can help a woman feel in control during this major life event.

No evidence justifies the routine use of enemas or shaving pubic hair. These are uncomfortable procedures that can be embarrassing for a woman and they have no role for routine use in modern childbirth.

Postdate Pregnancy

For a woman and her family who see the long anticipated due date come and go, pregnancy can begin to look like a permanent state. Patience usually pays off, and in 90 percent of cases, spontaneous onset of labor will occur before the 42 nd week. A postdate pregnancy is one that exceeds 42 weeks since the first date of the last menstrual period. The most common explanation is incorrect dating of the pregnancy, which again underscores how important it is to establish accurate dates early in the pregnancy. Of concern in the truly postdate pregnancy is the increased risk of uteroplacental insufficiency, oligohydramnios with umbilical cord compression, and the increasing size of the baby, which can make delivery more difficult.

It is common practice to assess fetal health in the postdate pregnancy by performing a nonstress test. This is performed using electronic fetal monitoring to assess the baby’s heart rate and expected acceleration with movement (reactivity). This test is reassuring if it shows the expected reactivity (at least two fetal heart rate accelerations of at least 15 beats/min lasting at least 15 sec over a 20-min period), but the specificity is low (lack of fetal heart rate reactivity does not always indicate a compromised fetus). Another common way to assess fetal health is a biophysical profile by ultrasound. This test assesses fetal movement and the amount of amniotic fluid present. It is a fairly reliable way of predicting fetal health. A modified biophysical profile

which is an ultrasound assessment of amniotic fluid in combination with the nonstress test, is as effective as a full biophysical profile in predicting fetal well-being Concerning findings with any of these antenatal tests may suggest that labor should be induced. In many settings it is common practice to induce labor at 42 weeks, even in the absence of concerning findings about fetal health. Factors including the “ripeness” of the cervix and the preferences of the pregnant woman should be considered in the decision to induce labor.

Summary

Prenatal care has played a role in reducing infant and maternal mortality and should be available to all pregnant women. Although the foundation of prenatal care is medical surveillance, attention should also be paid to psychosocial health, healthy behaviors, and preparation for labor and delivery. The philosophy toward prenatal care and childbirth is culturally dependent. The approach to childbirth can range from home births with little medical intervention to hospital births with use of multiple technologies. Regardlss of the approach, two tenets should be followed: (1) women’s choices should be honored as much as possible, and (2) any interventions should be proven effective before use.