Over the past 75 years, the number of U.S. women receiving prenatal care has steadily increased.1 Family physicians provide integrated prenatal care, including evidence-based screening, counseling, medical care, and psychosocial support. There is uncertainty about the critical elements of prenatal care and education, but inadequate care is associated with increased complications.2–4
Although women in developed countries often have seven to 12 prenatal visits, a multinational trial showed that decreasing the visits to a minimum of four did not increase adverse outcomes, although it slightly decreased patient satisfaction with care.5 Prenatal care that is provided by a small team; is coordinated; and follows an evidence-based, informed process results in fewer prenatal admissions, improved prenatal education, and greater satisfaction with care.6,7
|Physicians should attempt to obtain the most accurate dating of the pregnancy to assist in management of preterm labor and postterm pregnancy.
|6, 8, 9
|RhD-negative women carrying an RhD-positive fetus should be given Rho(D) immune globulin (RhoGam) to decrease the risk of alloimmunization.
|6, 11, 24
|Pregnant women with iron deficiency anemia should be offered treatment.
|6, 9, 26
|Folic acid supplementation should be recommended before conception.
|6, 9, 11, 16
|Women should be screened for rubella immunity during the first prenatal visit.
|6, 9, 11
|Pregnant women should be screened for asymptomatic bacteriuria between 11 and 16 weeks' gestation.
|6, 9, 11, 38
|Pregnant women should be offered inactivated influenza vaccination during influenza season.
|9, 11, 39
|Pregnant women should be offered group B streptococcus screening.
|9, 11, 41
|Pregnant women should be offered a glucose challenge test to screen for gestational diabetes between 24 and 28 weeks' gestation.
|9, 11, 54, 55, 56
|Women at risk of preterm birth should be offered intramuscular (preferred) or vaginal progesterone.
|11, 62, 63
|Breastfeeding should be recommended to pregnant women as the best feeding method for most infants.
|Counting fetal movement should not be recommended to pregnant women.
|Pregnant women should be screened for tobacco use, and individualized, pregnancy-tailored counseling should be offered to smokers.
|6, 9, 18
Physical Examination and Counseling
Standard elements of prenatal care include a routine physical examination (including pelvic examination) at the initial visit, maternal weight and blood pressure at all visits, fetal heart rate auscultation after 10 to 12 weeks with a Doppler monitor or after 20 weeks with a fetoscope, fundal height after 20 weeks, and fetal lie by 36 weeks.8,9 Table 1 includes components of routine prenatal visits.6,9–11
|Abdominal palpation (Leopold maneuvers) can be used to assess fetal presentation beginning at 36 weeks' gestation; it is less accurate earlier in pregnancy
|Blood pressure measurement6,9–11
|Although most guidelines recommend blood pressure measurement at each prenatal visit, further research is required to determine the optimal frequency
|Evaluation for edema6,10
|Edema is defined as greater than 1+ pitting edema after 12 hours of bed rest, or weight gain of 2.3 kg (5 lb) in one week
|Edema occurs in 80% of pregnant women and lacks specificity and sensitivity for diagnosing preeclampsia
|Fetal heart rate6,9–11
|Auscultation for fetal heart rate is recommended at each prenatal visit to confirm a viable fetus, although there is no evidence of other clinical or predictive value
|Fundal height measurement6,9–11
|Measurement of fundal height is recommended at each prenatal visit beginning at 20 weeks and should be plotted for monitoring purposes
|Measurement is subject to inter- and intraobserver error
|Some guidelines recommend routine dipstick urinalysis at each prenatal visit, whereas others no longer recommend it
|Testing does not reliably detect proteinuria in patients with early preeclampsia; trace glycosuria is unreliable for the detection of gestational diabetes
|Maternal height and weight should be measured at the first prenatal visit to determine body mass index, and weight should be measured at all subsequent visits
|Patients who are underweight or overweight have known risks, such as anemia and gestational diabetes, and counseling should be provided to guide optimal weight gain
A pelvic examination at the initial visit is useful in detecting reproductive tract abnormalities and to screen for sexually transmitted infections. Routine pelvimetry is not useful.11 Papanicolaou smears should be offered during prenatal care at recommended intervals based on age and Papanicolaou smear history, but do not need to be repeated during pregnancy.12 Although promotion of breastfeeding is critical, there is no clear evidence to support clinical breast examinations. However, breast examinations may help to proactively address breastfeeding concerns or problems.13 Although assessment of fundal height and fetal heart tones at every visit is recommended in multiple guidelines, the effect on outcomes is not clear.6,9,10
Early body mass index measurement, using prepregnancy height and weight, is important to guide further nutritional counseling and to address the risks of obesity and diabetes.14 Measurement of blood pressure at each prenatal visit will identify chronic hypertension and hypertensive disorders that may develop during pregnancy, such as preeclampsia and gestational hypertension.6 These disorders are often asymptomatic.
Periodontal disease is associated with increased risk of preterm birth, and an oral examination is often included in the first prenatal visit. However, treatment does not change outcomes.15
|Fruits and vegetables10
|Air travel generally is safe for pregnant women up to four weeks before the due date; however, long flights are associated with an increased risk of venous thrombosis
|Availability of medical resources at the destination should be considered
|The Centers for Disease Control and Prevention provides information for pregnant travelers at http://wwwnc.cdc.gov/travel/yellowbook/2012/chapter-8-advising-travelers-with-specific-needs/pregnant-travelers.htm
|Breastfeeding should be recommended as the best feeding method for most infants
|Breastfeeding contraindications include maternal human immunodeficiency virus infection, chemical dependency, and use of certain medications
|Structured behavior counseling, one-on-one needs-based counseling, and breastfeeding education programs increase breastfeeding success
|Childbirth education is a common part of prenatal care in the United States
|Although it may increase confidence, it does not change the experience of labor or birth outcomes
|At least 30 minutes of moderate exercise on most days of the week is a reasonable activity level for most pregnant women
|Pregnant women should avoid activities that put them at risk of falls or abdominal injuries
|Fetal movement counts6,9–11
|Routine counting of fetal movements should not be performed
|This has been shown to increase the patient's anxiety and results in more triage evaluations, prenatal testing, and interventions without improving outcomes
|Although hair dyes and treatments have not been explicitly linked to fetal malformation, they should be avoided during early pregnancy
|Exposure to heavy metals should be avoided during early pregnancy because of the potential for delayed fetal neurologic development
|Pregnant women should avoid herbal therapies with known harmful effects to the fetus, such as ginkgo, ephedra, and ginseng, and should be cautious of substances with unknown effects
|Hot tubs and saunas10,17
|Hot tubs and saunas should be avoided during the first trimester, because heat exposure during early pregnancy has been associated with neural tube defects and miscarriage
|Labor and delivery9,10
|Pregnant women should be counseled about what to do when their membranes rupture, what to expect when labor begins, strategies to manage pain, and the value of having support during labor
|Medications (prescription and over-the-counter)6,9,10
|Risks and benefits of individual medications should be reviewed
|Few medications have been proven safe for use during pregnancy, particularly during the first trimester
|Pregnant women should avoid ionizing radiation, because it may affect fetal thyroid development
|Adverse fetal effects are not associated with radiography that is in a normal diagnostic range (less than 50 mGy) and that avoids direct abdominal views; ultrasonography; or use of microwaves, computers, or cell phones
|Pregnant women should use a three-point seat belt
|Less than one-half of pregnant women use a seat belt, and less than one-third receive physician counseling about seat-belt use
|Most women may continue to have sex during pregnancy; however, in certain situations (e.g., placenta previa), avoiding sex is generally recommended
|Pregnant women should avoid exposure to solvents, particularly in areas without adequate ventilation
|Exposure to solvents has been associated with an increase in miscarriage rates
|Pregnant women should be screened for alcohol use; no amount of alcohol consumption has been proven safe during pregnancy
|Counseling is effective in decreasing alcohol consumption in pregnant women and associated infant morbidity
|Pregnant women should be informed of the potential adverse effects of illicit drug use on the fetus
|Pregnant women who use illicit drugs often require specialized interventions
|Admission to a detoxification program may be indicated, as well as methadone therapy in women addicted to opiates
|Pregnant women should be screened for tobacco use, and individualized, pregnancy-tailored counseling should be offered to smokers
|Smoking cessation counseling and multicomponent strategies are effective in decreasing the incidence of low-birth-weight infants
|Although working in general is safe during pregnancy, some working conditions, such as prolonged standing and exposure to certain chemicals, are associated with pregnancy complications
Dating of Pregnancy and Routine Ultrasonography
Accurate dating as early as possible in the pregnancy is important for scheduling screening tests and planning for delivery.6–9 Estimated date of confinement is based on the first day of the last menstrual period plus 280 days. Urine pregnancy tests qualitatively test for beta subunit of human chorionic gonadotropin and are usually positive within one week of missed menses.19
Early ultrasonography should be performed if the patient has irregular cycles or bleeding, if the patient is uncertain of the timing of her last menstrual period, or if there is a discrepancy in the size of her uterus compared with the gestational age. Ultrasonography can accurately date the pregnancy, evaluate for multiple gestation, and reduce the likelihood of unnecessary labor induction for postterm pregnancy.20,21 Ultrasound dating is considered accurate to within four to seven days in the first trimester, 10 to 14 days in the second trimester, and 21 days in the third trimester.9,21 Pregnancy dating should be confirmed with auscultation of fetal heart tones between 10 and 12 weeks, and with fetal quickening between 16 and 18 weeks in women who have been pregnant before or between 18 and 19 weeks in first pregnancies.
A randomized trial comparing routine screening ultrasonography (between 15 and 22 weeks and again at 31 to 35 weeks) performed only for medical indications showed no difference in perinatal outcomes (e.g., fetal or neonatal death, neonatal morbidity).22 A recent Cochrane review, however, showed that ultrasonography before 24 weeks reduces missed multiple gestation and inductions for postterm pregnancies.21 There is no other scientific support for routine ultrasonography in uncomplicated pregnancies. It is the standard of care in most U.S. communities to offer a single ultrasound examination at 18 to 20 weeks' gestation, even if dating confirmation is not needed.11 This is the optimal time for fetal anatomic screening,23 although the sensitivity of ultrasonography for structural anomalies is poor (overall sensitivity from 11 studies = 24.1%, range = 13.5% to 85.7%).6
The risk of developing alloimmunization for an RhD-negative woman carrying an RhD-positive fetus is approximately 1.5%. This risk can be reduced to 0.2% with Rho(D) immune globulin (RhoGam).6,11,24 Testing for ABO blood group and RhD antibodies should be performed early in pregnancy. Rho(D) immune globulin, 300 mcg, is recommended for nonsensitized women at 28 weeks' gestation, and again within 72 hours of delivery if the infant has RhD-positive blood.25
Rho(D) immune globulin should also be administered if the risk of fetal-to-maternal transfusion is increased (e.g., with chorionic villus sampling, amniocentesis, external cephalic version, abdominal trauma, or bleeding in the second or third trimester). Although alloimmunization is uncommon before 12 weeks' gestation, women with a threatened early spontaneous abortion may be offered Rho(D) immune globulin, 50 mcg. 25
The U.S. Preventive Services Task Force has found insufficient evidence to recommend for or against routine iron supplementation.27 Multivitamins alone have demonstrated no benefit over iron and folate supplementation.28 Pregnant women with anemia other than iron deficiency or who do not respond to iron supplementation within four to six weeks should be evaluated for other conditions, including malabsorption, ongoing blood loss, thalassemia, or other chronic diseases.
Genetic Testing and Neural Tube Defects
Down syndrome (trisomy 21 syndrome) occurs in one per 1,440 births in women 20 years of age and one per 32 births in women 45 years of age.29 Most organizations recommend that all pregnant women be offered aneuploidy screening. Traditional serum screening for Down syndrome is complicated by high false-positive rates (90% to 95% of positive results are false). False-negative results are also possible. Patients should be given sufficient information to make an informed decision.30
Invasive genetic testing (amniocentesis or chorionic villous sampling) should be offered to women who are 35 years or older. At 35 years of age, the risk of Down syndrome (one per 338 births) is similar to that of fetal loss due to amniocentesis.29 It is common to offer invasive testing to women 35 years and older without first performing screening tests; however, screening tests can be used for risk stratification to help a woman decide if she wants invasive testing.6,11 Options for aneuploidy screening include nuchal translucency testing with serum testing (nine to 11 weeks' gestation) and later serum testing alone (15 to 19 weeks' gestation). There are a variety of combinations of such tests, and results are generally reported as the risk of aneuploidy. All screening tests have a positive rate of approximately 5% (most of which are false positives) and a detection rate of 69% to 87%.6,11 Table 4 compares screening tests for Down syndrome.29
|Term risk cutoff
|Positive predictive value (%)
|First trimester screening
|Nuchal translucency, free β-hCG, PAPPA, maternal age
|1 in 325
|Quadruple screening (second trimester)
|Unconjugated estriol, α-fetoprotein, free β-hCG, inhibin A, maternal age
|1 in 385
|Integrated screening (first and second trimesters)
|Nuchal translucency, PAPPA, α-fetoprotein, unconjugated estriol, free β-hCG/total hCG, inhibin A, maternal age
|1 in 200
If a screening test is positive for Down syndrome, the woman should be offered amniocentesis (15 weeks' gestation or later) or chorionic villous sampling (11 to 13 weeks). The rates of excess fetal loss with these two procedures are similar.29 In centers where both procedures are available, women can consider earlier genetic testing options.6,11
A combination of serum and nuchal translucency testing can also screen for other trisomy syndromes, such as 13 and 18. Most laboratories can report the risk of trisomy 18 syndrome using serum testing. Protocols for the detection of other trisomies can detect a large portion of these anomalies. These protocols have lower sensitivities (60%) and higher specificities (99%), but similar positive predictive values or rates of false positives, compared with protocols for trisomy 21 screening, because these conditions are much more rare.29
A new technology, noninvasive prenatal diagnosis, offers the possibility of screening for aneuploidies and other conditions by identifying fragments of fetal DNA in maternal circulation. Early studies have shown a sensitivity for Down syndrome of 100% and a specificity of 99.3%.31 Currently, cost is high and insurance coverage variable, but this may represent an emerging step in sequential genetic testing.
Other genetic screening should be based on the family histories of the patient and her partner. Genetic risk considerations include cystic fibrosis in whites; Tay-Sachs disease in Ashkenazi Jews, Cajuns, and French Canadians; Canavan disease in Ashkenazi Jews; sickle cell disease in Africans; and thalassemias in Africans, East Indians, Hispanics, Mediterraneans, Middle Easterners, and Southeast Asians.6,10,11
Neural tube defects affect 1.5 per 1,000 pregnancies and can be detected by testing maternal serum α-fetoprotein levels (sensitivity = 85.7%, specificity = 97.6%).6 Folic acid supplementation should be recommended early, preferably before conception.6,9,11,16 Folic acid, 400 mcg daily, started before pregnancy and continued until six to 12 weeks' gestation reduces the rate of neural tube defects by nearly 75%.6 Women taking folic acid antagonists or who have a history of carrying a fetus with a neural tube defect should take 4 mg of folic acid daily.16
Thyroid-stimulating hormone levels should be measured in women with a history of thyroid disease or symptoms of disease in pregnancy, although there is no evidence that universal testing during pregnancy improves outcomes.32 There is concern that subclinical hypothyroidism in pregnant women may increase the risk of neurodevelopmental delays in infants, but the effectiveness of levothyroxine therapy has not been demonstrated.33 A large randomized trial comparing thyroid-stimulating hormone measurement before 16 weeks' gestation and after birth found no differences in children's IQ scores at three years of age.34 If the thyroid-stimulating hormone level is abnormal, a free thyroxine test may be useful.
Women with overt hypothyroidism, which complicates one to three per 1,000 pregnancies, are at increased risk of pregnancy loss, preeclampsia, low birth weight, and fetal demise or stillbirth. Hyperthyroidism occurs in two per 1,000 pregnancies and is associated with pregnancy loss, preeclampsia, low birth weight, thyroid storm, prematurity, and congestive heart failure.32
Universal screening for bacterial vaginosis is not supported by current evidence. A recent systematic review found that screening and subsequent treatment of infection does not prevent delivery before 37 weeks' gestation, but decreases the risk of low birth weight and premature rupture of membranes.35
Women should be screened for rubella immunity during the first prenatal visit, ideally before conception when vaccination is safe. All women who are nonimmune should be offered vaccination postpartum to prevent congenital rubella syndrome in subsequent pregnancies. Vaccination should not be given during pregnancy, but may be given during lactation.6,9,11
Maternal varicella (chickenpox) can have significant fetal effects, including congenital varicella syndrome (low birth weight and limb, ophthalmologic, and neurologic abnormalities) and neonatal varicella; infection can occur from approximately five days before to two days after birth. Maternal shingles is not a risk for the infant because of passive maternal immunity. There is some evidence to support assessing the mother's varicella history at the first prenatal visit, with serologic testing for those with a negative history. Women who test negative for immunoglobulin G should avoid exposure to varicella during pregnancy and be offered vaccination postpartum.36 After a significant exposure, varicella-zoster immune globulin therapy may be considered if available.37
TETANUS AND PERTUSSIS
Women should receive a diphtheria, tetanus, and pertussis (Tdap) vaccine during each pregnancy. The best time for vaccination is between 27 and 36 weeks' gestation for antibody response and passive immunity to the fetus; however, the vaccine may be given any time during pregnancy.39
GROUP B STREPTOCOCCUS
Group B streptococcus causes significant neonatal morbidity and mortality, particularly among premature infants, and all pregnant women should be offered screening.9,11,41 Increased screening at 35 to 37 weeks' gestation and treatment with intrapartum antibiotic prophylaxis (penicillin, or clindamycin if allergic) for those who are positive (10% to 30%) have decreased neonatal mortality in the past decade.41 Intrapartum treatment is also recommended for women with group B streptococcus bacteriuria occurring at any stage of pregnancy, and for women with unknown group B streptococcus status and risk factors (e.g., preterm birth before 37 weeks' gestation, rupture of membranes more than 18 hours before delivery, or intrapartum fever), and for women with a history of group B streptococcus bacteriuria during pregnancy.41
SEXUALLY TRANSMITTED INFECTIONS
|Universal (Centers for Disease Control and Prevention)
|Azithromycin (Zithromax), erythromycin, amoxicillin, clindamycin
|Congenital eye infections and pneumonia, preterm birth
|Targeted (U.S. Preventive Services Task Force)
|Screening not indicated, diagnosis is clinical
|Consider cryotherapy or trichloroacetic acid
|Vertical transmission, self-limited and usually minor; treatment may not affect transmission
|Based on personal or geographic risk
|Chorioamnionitis, preterm birth, low birth weight, congenital eye infections
|Active and passive immunization of the infant
|Screening not indicated
|Acyclovir (Zovirax) or famciclovir (Famvir) prophylaxis starting at 36 weeks' gestation for women with a history of herpes infection
|Vertical transmission (consider cesarean delivery for women with active lesions at delivery)
|Consider culture or polymerase chain reaction testing of lesions
|Human immunodeficiency virus42
|Universal (patient may opt out)
|Consider repeat screening in the third trimester
|Universal rapid plasma reagin or Venereal Disease Research Laboratories testing
|Penicillin G benzathine
|Consider repeat testing at 28 weeks' gestation
|Screening not indicated
|Preterm birth, premature rupture of membranes, low birth weight
Domestic violence during pregnancy increases the risk of complications, such as spontaneous abortion, placental abruption, premature rupture of membranes, low birth weight, and prematurity.49 Domestic violence–related homicide is the leading cause of death among pregnant women in the United States.49
The U.S. Preventive Services Task Force (USPSTF) recommends that clinicians screen women of childbearing age for intimate partner violence, such as domestic violence, and provide intervention services or a referral if a woman screens positive.50 Family physicians should be aware of the signs of abuse in pregnant women, the effect of violence on health, and the increased risk of child abuse after delivery.51
The American College of Obstetricians and Gynecologists (ACOG) supports depression screening during pregnancy.52 Perinatal depression is underdiagnosed and complicates 10% to 15% of pregnancies, resulting in significant morbidity for the mother and infant. Complications include prematurity, low birth weight, neurodevelopmental delays, and issues with maternal/infant bonding.
A number of screening tools are available with similar validity and sensitivity. Untreated depression may result in poor prenatal care; inadequate nutrition; and increased alcohol, drug, and tobacco use.53
Complications of Pregnancy
Gestational diabetes complicates 2% to 5% of pregnancies and is associated with hypertensive disorders, macrosomia, shoulder dystocia, and cesarean deliveries.9,11 In addition, the increasing prevalence of undiagnosed type 2 diabetes mellitus and insulin resistance in the general population means many women will first show signs of diabetes during pregnancy. Screening protocols, diagnostic criteria, and treatment criteria are controversial, but diagnosing diabetes earlier in pregnancy and decreasing hyperglycemia improves some pregnancy outcomes.54 ACOG, in collaboration with the USPSTF, recommends screening for overt diabetes early in pregnancy in those who are at risk (i.e., previous history of gestational diabetes, obesity, or known glucose intolerance) using A1C or fasting blood glucose levels, and screening in all pregnant women at 24 to 28 weeks' gestation with a 50-g glucose load. An abnormal one-hour test result should be followed by confirmatory testing with a three-hour glucose tolerance test.55,56 In contrast, the National Institute for Health and Clinical Excellence has found insufficient evidence to recommend for or against screening for gestational diabetes.6 In the United States, most women are screened one hour after a 50-g glucose challenge.57 Selective screening has been shown to miss gestational diabetes in up to one-half of women.55
HYPERTENSION IN PREGNANCY
Blood pressure is generally monitored at each prenatal visit, and women should be counseled on warning signs of preeclampsia. For women who had chronic or severe hypertension in a previous pregnancy, baseline urine protein and preeclampsia laboratory testing may be helpful.58 Preeclampsia in a previous pregnancy, chronic hypertension, and low dietary calcium (less than 700 mg) increase the risk of preeclampsia. Calcium supplementation for women with low dietary calcium reduces the risk of preeclampsia by 30% to 50%.59 Low-dose aspirin from 12 to 36 weeks' gestation reduces preeclampsia by 20% in women with a history of preeclampsia, chronic hypertension, diabetes, autoimmune disease, or renal disease, or in women with current gestational hypertension.60
Preterm birth (before 37 weeks' gestation) is a significant cause of neonatal morbidity and mortality, with more than 500,000 preterm births annually in the United States.61 Progesterone (preferably weekly injections administered from 16 to 37 weeks' gestation; daily vaginal suppositories are an alternative) reduces preterm birth by approximately 35% in women with a history of spontaneous preterm labor or premature rupture of membranes.11,62,63 Cervical cerclage may reduce the risk of preterm birth in women with a previous preterm birth and a short cervix, although the evidence is mixed.64 Recent studies have shown a significant reduction in preterm birth with vaginal progesterone among women with an asymptomatic short cervix identified on ultrasonography.65 Smoking cessation and treatment of genital infections may also reduce the risk of preterm birth.
A Cochrane review of induction at 41 weeks' gestation versus expectant management to 42 weeks' gestation concluded that perinatal death was less common among women induced at 41 weeks, although it was rare in both groups.66 The rate of perinatal death was 1.7 per 1,000 in the expectant management group versus 0.5 per 1,000 in the induction group (the number needed to treat with induction to prevent one perinatal death was 410 women).66 The rate of meconium aspiration syndrome and cesarean delivery were lower with induction. Operative vaginal delivery was slightly more common among women induced at 41 weeks. Women should be counseled about the risks and benefits of both approaches.
Although there is no evidence that prenatal testing decreases perinatal death with postterm pregnancy, the standard of care is twice-weekly nonstress testing and weekly assessment of amniotic fluid volume beginning at 41 weeks' gestation.6 Physicians should recommend induction of labor for oligohydramnios (amniotic fluid index less than 5 mL or maximum vertical pocket less than 2 cm at term). A nonreactive, nonstress test is usually followed by a biophysical profile, a contraction stress test, or umbilical artery Doppler.67 If these tests are not reassuring after 41 weeks' gestation, physicians should recommend induction of labor.9
Data Sources: We identified guidelines/studies from PubMed, Cochrane Database of Systematic Reviews, Institute for Clinical Systems Improvement, USPSTF, ACOG, Society of Obstetricians and Gynaecologists of Canada, and Royal College of Obstetricians and Gynaecologists. We searched prenatal care with randomized controlled trial, evidence-based review, meta-analysis, and systematic review. We also searched pregnancy with physical exam, ultrasound, dating, alloimmunization, anemia, genetic testing, trisomy 21, and thyroid. Search dates: November 1, 2011, and December 2, 2013.