INTRODUCTION — The goal of prenatal care is to ensure the birth of a healthy baby with minimal risk for the mother. Prenatal care is not a single intervention; instead, it represents a series of assessments, discussions, and interventions over time that are variously applied by different practitioners. The "quality" of prenatal care and the effect of individual components on outcome are thus difficult to measure.

After the initial prenatal visit, prenatal care is directed at ongoing evaluation of the health status of both mother and fetus, ongoing counseling about pre- and postpartum issues, anticipation of problems, and intervention, if possible, to prevent or minimize morbidity. This topic will discuss prenatal care in the second and third trimesters. Prenatal issues related to the first visit and first trimester are reviewed separately (see "Prenatal care: Initial assessment"). Specific issues related to prenatal care for women with multiple gestations are also reviewed separately. (See "Twin pregnancy: Overview" and "Triplet pregnancy".)

COVID-19 — The American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine have issued guidance regarding prenatal care during the coronavirus disease 2019 (COVID-19) pandemic (available at acog.org and SMFM.org) [1,2]. It includes general guidance for testing and preventing spread of COVID-19 and suggestions for modifying traditional protocols for prenatal visits (eg, reduced number, timing, test grouping, visitor policy), obstetric ultrasound examinations, and use of nonstress tests and biophysical profiles. (See "COVID-19: Overview of pregnancy issues", section on 'Prenatal care'.)

FREQUENCY OF PRENATAL VISITS — Observational data suggest that prenatal care saves lives and show an association between the number of prenatal visits and/or early gestational age at the initiation of care and pregnancy outcomes, after controlling for confounding factors (eg, length of gestation) [3,4]. However, there are limited data as to what constitutes the optimal number and frequency of prenatal visits, or the optimal content of those visits.

In the United States, the typical intervals for prenatal visits for nulliparous women with uncomplicated pregnancies are every 4 weeks until 28 weeks of gestation, every 2 weeks from 28 to 36 weeks, and then weekly until delivery [5]. Parous women with uncomplicated medical and obstetric histories may be seen less frequently. Women with problems are seen more frequently, depending on the nature of the problems. According to this schedule, a woman with an uncomplicated pregnancy in which the first visit is at six weeks of gestation and the last visit is at 41 weeks will have 16 prenatal visits.

While the standard prenatal visit schedule in the United States is commonly followed, it requires significant effort and planning on the part of the patient without clear evidence of benefit. For example:

●In a cohort study of over 7200 women with low-risk pregnancies, there were no differences in neonatal intensive care unit admissions, five-minute Apgar score <7, neonatal demise, or small for gestational age infants among women who had more than 10 prenatal visits and those who had 10 or fewer prenatal visits [6]. The women in the high utilization group were 33 percent more likely to undergo induction of labor and 50 percent more likely to have a cesarean delivery than the women in the low utilization group, but data are insufficient to conclude a causal relationship.

●For women with high risk pregnancies by various criteria, randomized trials comparing routine with enhanced prenatal care (eg, extra office visits, health education, home visits, telephone contact, psychosocial support) have not reported significantly improve outcome with enhanced care [7,8].

The National Institute of Health and Clinical Excellence (NICE) suggests a reduced frequency of visits: 10 appointments for nulliparous women and 7 appointments for parous women, and each visit should have a specific purpose/goal [9]. This approach takes into account the cost and time constraints of modern society and lack of proven efficacy of frequent prenatal visits in randomized trials.

The 2016 World Health Organization (WHO) antenatal care guidelines suggest a minimum of eight antenatal visits for all women, regardless of parity [10]. The WHO advises one visit in the first trimester, two in the second trimester, and five in the third trimester. This represents a four-visit increase from prior recommendations in response to a 2015 systematic review that reported a 15 percent increase in perinatal deaths for women with low risk pregnancies in middle- and lower-income countries who had reduced antenatal visits (typically fewer than five visits) compared with more visits [4].

Higher risk pregnancies — A healthy woman with an uncomplicated pregnancy is generally considered low risk. Although there is no precise definition for higher risk pregnancy, it generally includes women who do not meet the definition of low risk because of medical or surgical conditions, past or current obstetric complications, or social or demographic factors (eg, old or young maternal age, lack of social support, grand multiparity [≥4 to 6 births]). There is consensus that these women need additional care during pregnancy [9]. The nature and frequency of the additional care depends on individual factors.

SIGNS AND SYMPTOMS THAT SHOULD BE REPORTED TO THE HEALTH CARE PROVIDER — Pregnant women should be counseled about signs and symptoms that should be reported to their health care provider promptly. These include, but are not limited to:

●Vaginal bleeding – (See "Overview of the etiology and evaluation of vaginal bleeding in pregnancy".)

●Leakage of fluid per vagina – (See "Preterm prelabor rupture of membranes: Clinical manifestations and diagnosis".)

●Decreased fetal activity – (See "Decreased fetal movement: Diagnosis, evaluation, and management".)

●Signs and symptoms of preterm labor (eg, low backache; increased uterine activity compared with previous patterns; menstrual-like cramps; diarrhea; increased pelvic pressure; vaginal leaking of clear fluid, spotting or bleeding, contractions). (See "Preterm labor: Clinical findings, diagnostic evaluation, and initial treatment".)

●Signs and symptoms of preeclampsia (eg, headache not responsive to one dose of acetaminophen, visual changes, persistent epigastric or right upper quadrant abdominal pain). (See "Preeclampsia: Clinical features and diagnosis".)

As in any patient group, signs and symptoms suggestive of a medical or surgical disorder should be reported.

DEPRESSION SCREENING — There is consensus that pregnant women should be assessed at least once during pregnancy or the postpartum period for depression and anxiety symptoms using a validated screening tool [11,12]. Of the screening tools, the Edinburgh Postnatal Depression Scale is commonly used as it is a validated questionnaire that takes fewer than five minutes to complete, is easy to score, and has been translated into at least 12 languages (figure 1 and figure 2). It assess symptoms related to both depression and anxiety.

There is no consensus as to the optimal time to perform this screen and significant variation exists among obstetric practices. Women who screen positive are then referred for further evaluation and counseling. Other screening tools are described separately. (See "Unipolar major depression during pregnancy: Epidemiology, clinical features, assessment, and diagnosis", section on 'Screening'.)

ONGOING ASSESSMENTS — Routine assessments at each prenatal visit typically consist of:

●Measurement of blood pressure – The procedure for checking blood pressure is generally similar to that in nonpregnant women. (See "Treatment of hypertension in pregnant and postpartum patients", section on 'Technique for accurate measurement of blood pressure'.)

Blood pressure decreases slightly in the second trimester and then rises slightly at term in normal pregnancies (defined as no essential hypertension, preeclampsia, or diabetes and delivery of an appropriate size for gestational age infant at term) (figure 3). (See "Maternal adaptations to pregnancy: Cardiovascular and hemodynamic changes", section on 'Blood pressure and vascular resistance'.)

Measurement of blood pressure is necessary for diagnosis of hypertension, but no mean arterial pressure, systolic blood pressure, or diastolic blood pressure threshold in early pregnancy performs well for predicting future development of preeclampsia or gestational hypertension [13]. (See "Early pregnancy prediction of preeclampsia", section on 'All women: Routine blood pressure measurement in pregnancy'.)

●Measurement of weight – Gestational weight gain can impact pregnancy outcome. Weight gain targets depend on the woman’s baseline weight (table 1). (See "Gestational weight gain", section on '2009 IOM weight gain recommendations'.)

●Urine dipstick for protein, although the value of this test is questionable in women with normal blood pressure [14-17].

●Assessment of fetal growth in the second and third trimesters either through measurement of fundal height or by ultrasound evaluation for women with risk factors for intrauterine growth restriction. (See 'Screen for fetal growth restriction' below.)

●Documentation of fetal heart rate.

●Assessment of maternal perception of fetal activity (in the second and third trimesters).

●Assessment of fetal presentation (in the third trimester).

●Assessment of significant events since prior visit, such as recent travel, illness, stressors, or exposure to infection (eg, Zika virus or severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2]) etc. (See "Zika virus infection: Evaluation and management of pregnant women" and "COVID-19: Overview of pregnancy issues".)

●Review of signs and symptoms of potential pregnancy problems. (See 'Signs and symptoms that should be reported to the health care provider' above.)

These simple, noninvasive, inexpensive assessments detect up to 50 percent of fetuses with growth abnormality, prevent 70 percent of eclampsia by early detection of preeclampsia [16], and identify 80 percent of breech presentations prior to labor when external cephalic version can be performed to decrease the need for cesarean delivery [18-20].

Ongoing assessment of gestational weight gain, as well as ongoing discussion of diet and exercise, may help prevent excessive weight gain during pregnancy and overweight or obesity postpartum. (See "Gestational weight gain".)

PERIODIC ASSESSMENTS AND PROCEDURES — Prenatal screening should be performed early within recommended intervals to allow adequate time for follow-up of screening tests, performance of diagnostic tests, counseling about test results, and discussion of management options, including termination of pregnancy if the patient chooses this approach.

First trimester — First-trimester screening and diagnostic testing may include tests for:

●Red cell (RBC) antibodies

●Current or past infection (eg, sexually transmitted infections [STI], bacteriuria, rubella immunity, varicella immunity)

●Inherited disorders (eg, cystic fibrosis, fragile X, spinal muscular atrophy, hemoglobinopathy)

●Fetal aneuploidy (eg, trisomy 21)

●Thyroid disease

●Elevated lead level

Screening and diagnostic testing performed at the first prenatal visit or later in the first trimester are reviewed in detail separately. (See "Prenatal care: Initial assessment", section on 'Laboratory tests'.)

15 to 24 weeks of gestation

Screen for neural tube defects — For women who choose to undergo screening for neural tube defects, maternal serum alpha-fetoprotein and ultrasound examination are both effective methods; ultrasound examination is generally the preferred approach. (See "Open neural tube defects: Risk factors, prenatal screening and diagnosis, and pregnancy management".)

Screen for trisomy 21 — For women who book their first prenatal appointment in the second trimester or choose to undergo Down syndrome (trisomy 21) screening in the second trimester, the most common test is the quadruple test (ie, level of alpha-fetoprotein [AFP], unconjugated estriol [uE3], human chorionic gonadotropin [hCG], and inhibin A in maternal serum between 15 and 22 weeks of gestation). Cell free DNA screening is another option. (See "Down syndrome: Overview of prenatal screening".)

Screen for fetal anomalies — For women who choose to undergo ultrasound screening for fetal structural anomalies, the procedure is optimally performed in the second trimester, between 18 and 22 weeks of gestation [9]. Although many congenital anomalies can be identified in the first trimester, sensitivity is higher in the second trimester. Additional and follow-up testing may be needed to confirm the suspected diagnosis.

Meta-analyses of randomized trials evaluating the utility of routine prenatal ultrasound examination have reported the following findings. The included trials were generally of low or moderate quality. Compared with selective use, routine ultrasound examination in early pregnancy (by 24 weeks of gestation) [21]:

●Improved detection of multiple gestation (3 versus 39 percent of multiple gestations not found, risk ratio [RR] failure to detect a multiple gestation 0.07, 95% CI 0.03-0.17).

●Improved detection of a major fetal abnormality (15.3 versus 4.4 percent detected, RR 3.46, 95% CI 1.67-7.14).

●Improved gestational dating, resulting in fewer inductions for postterm pregnancy (1.8 versus 3.1 percent induction rate, RR 0.59, 95% CI 0.42-0.83).

However, perinatal death (stillbirth after trial entry, death of a live born infant up to 28 days of age) was similar for routine and selective examination groups (0.7 versus 0.8 percent, RR 0.89, 95% CI 0.70-1.12).

A number of factors (eg, gestational age at examination, type of malformation, number of ultrasounds performed, operator experience, quality of equipment, population characteristics) affect detection rates, and were not addressed in the meta-analysis.

Screen for short cervix — A short cervical length (≤25 mm) on transvaginal ultrasound between 16 and 24 weeks of gestation is associated with an increased risk for spontaneous preterm birth. Cervical length can be measured when the patient undergoes ultrasound examination for fetal anomalies. There is insufficient evidence to mandate a policy of routine cervical length screening between 16 and 24 weeks for all pregnancies [22]; however, in randomized trials, interventions such as treatment with vaginal progesterone have reduced the rate of subsequent preterm birth [23]. Screening, diagnosis, and management of short cervix are discussed in detail separately. (See "Short cervix before 24 weeks: Screening and management in singleton pregnancies".)

24 to 28 weeks of gestation

Screen for gestational diabetes — In the United States, universal screening for gestational diabetes is recommended at 24 to 28 weeks of gestation. Earlier screening should be considered in women with significant risk factors (eg, gestational diabetes in a prior pregnancy, family history of diabetes in a first-degree relative). (See "Gestational diabetes mellitus: Screening, diagnosis, and prevention".)

A risk factor-based approach to 24 to 28 week screening is used in some countries [9] but is less effective.

Administer anti-D immune globulin to RhD-negative women — In RhD-negative women, RBC antibody screening is repeated at 28 weeks of gestation, and anti-D immune globulin is administered. Although there is good evidence that administration of anti-D immune globulin is cost-effective, there are no data that establish the cost-effectiveness of repeat antibody screening at this time if the initial antibody screening was negative. (See "RhD alloimmunization in pregnancy: Overview" and "RhD alloimmunization: Prevention in pregnant and postpartum patients".)

In RhD-positive women who had a negative RBC antibody screen early in pregnancy, rescreening for RBC antibodies in the third trimester is not cost-effective. (See "Management of non-RhD red blood cell alloantibodies during pregnancy".)

Screen for anemia — The hemoglobin or hematocrit should be checked early in the third trimester to screen for anemia. Increased iron and folate requirements of pregnancy may result in anemia, which can usually be corrected before delivery by appropriate supplementation. Evaluation and treatment of anemia are reviewed separately. (See "Anemia in pregnancy".)

Anemia in late pregnancy is defined as follows [24]:

●Second trimester – Hemoglobin level <10.5 g/dL (approximate hematocrit <32 percent)

●Third trimester – Hemoglobin level <11 g/dL (approximate hematocrit <33 percent)

These values are based on data derived from an iron-supplemented population.

28 to 36 weeks of gestation

Screen for sexually transmitted infections — The CDC recommends testing for STIs (eg, HIV, syphilis, chlamydia, gonorrhea) in the third trimester (28 to 36 weeks) in women at increased risk (table 2) [25].

The value of repeated testing is supported by a retrospective study of STI test results in 1.3 million pregnant women in the United States [26]. Among women who tested positive for chlamydia or gonorrhea at least once during pregnancy and were retested before delivery, the last prenatal test was positive in 6 percent (969/16,039) of women previously testing positive for chlamydia and 3.8 percent (100/2610) of women previously testing positive for gonorrhea. Among women aged 16 to 24 or 25 years who tested negative at the first prenatal visit but were at increased risk for acquiring a STI, 3.4 percent (1746/50,959) had a subsequent positive test for chlamydia and 1.1 percent (564/51,077) had a subsequent positive test for gonorrhea.

In some areas, repeat testing for syphilis and HIV is mandatory (see "Syphilis in pregnancy"). Retesting for HIV using an opt-out approach in the third trimester (≤36 weeks of gestation) is recommended for women at increased risk for acquiring HIV infection, women residing in or receiving care in areas of high HIV prevalence, symptomatic women (eg, fever, lymphadenopathy, skin rash, myalgias, arthralgias, headache, oral ulcers, leukopenia, thrombocytopenia, elevated transaminases), incarcerated women, and women who declined testing earlier in pregnancy [25,27]. The basis of this recommendation is that appropriate intervention peripartum can significantly reduce perinatal transmission. A conventional or rapid test can be used in the third trimester. (See "Prenatal evaluation of women with HIV in resource-rich settings" and "Antiretroviral selection and management in pregnant women with HIV in resource-rich settings" and "Screening and diagnostic testing for HIV infection".)

Screen for fetal growth restriction — Ongoing clinical assessment of fetal growth is a routine component of prenatal care. (See "Fetal growth restriction: Screening and diagnosis", section on 'Screening'.)

Sonographic assessment of fetal growth is indicated in the third trimester for those pregnancies at high risk of fetal growth restriction (see "Fetal growth restriction: Screening and diagnosis" and "Fetal growth restriction: Evaluation and management"). Although early identification of growth-restricted fetuses allows for closer surveillance and earlier intervention in case of decompensation, the use of ultrasound in the third trimester to screen for fetal growth disturbance in low risk women has not been effective for reliably detecting these fetuses or improving outcome.

●A 2015 Cochrane review of controlled trials of routine ultrasound >24 weeks versus no/concealed/selective ultrasound >24 weeks of gestation found routine ultrasound did not improve detection of neonates with birth weight <10^th percentile (RR 0.98, 95% CI 0.74-1.28, four trials, n = 20,293) or decrease perinatal mortality (RR 1.13, 95% CI 0.58-2.19, six trials, n = 28,133) [28].

●Subsequently, a prospective cohort study (Pregnancy Outcome Prediction study) specifically addressed this issue in a population of unselected nulliparous women with singleton gestations who underwent routine early ultrasonography for pregnancy dating [29]. Women who agreed to participate (n = 4512) were scheduled to undergo serial ultrasound examinations at approximately 20, 28, and 36 weeks of gestation, but findings from the research component of these ultrasound scans (uteroplacental Doppler, biometry, estimated fetal weight [EFW]) were masked from both the women and their providers. Approximately one-half of the women eventually underwent clinically indicated third-trimester ultrasound examinations.

Universal sonography in the third trimester almost tripled the detection of infants subsequently born small for gestational age (SGA) compared with clinically indicated sonography (57 versus 20 percent); however, universal ultrasound overdiagnosed SGA more often than clinically indicated ultrasound (positive predictive value 35 versus 50 percent).

The study also evaluated whether universal antenatal screening for SGA improved perinatal outcome. Among fetuses with EFW <10^th percentile, only those with abdominal circumference (AC) growth velocity at the lowest decile were at increased risk for neonatal morbidity. Umbilical artery pulsatility index in the highest decile did not distinguish between SGA infants at low risk and high risk of neonatal morbidity.

●In addition, a randomized trial of routine third-trimester ultrasound (at both 28 to 30 and 34 to 36 weeks) versus usual care (clinically indicated ultrasound only) in over 13,000 low-risk pregnancies found that the intervention prenatally detected more infants who were SGA at birth (32 versus 19 percent of SGA infants were identified prenatally), but the sensitivity of routine ultrasound was still quite low, and the frequency of severe adverse perinatal outcomes was similar in both the intervention and usual care groups (<2 percent) [30]. A limitation of the trial was that, prenatally, the authors used AC <10 percent or slow growth of the AC to identify growth restriction, but their neonatal outcome for SGA was birth weight less than 10 percent.

Determine the appropriate approach for antenatal fetal surveillance — All pregnant women should be aware of fetal movement, either subjectively or using a kick count method, and notify their provider if fetal movement decreases. (See "Decreased fetal movement: Diagnosis, evaluation, and management".)

Antenatal fetal testing using the nonstress test or biophysical profile is indicated in pregnancies in which the risk of antepartum fetal demise is increased. This testing is usually initiated in the third trimester at 32 weeks, but may be initiated earlier if the fetus is believed to be at increased risk of death and delivery or another intervention is an option. (See "Overview of antepartum fetal assessment", section on 'Indications for fetal assessment'.)

Offer external cephalic version of noncephalic fetal presentations — For pregnancies with breech presentation, we offer external cephalic version (ECV) at 36 weeks of gestation. Randomized trials have shown that ECV of the breech fetus is an effective procedure for increasing the chance of cephalic presentation at onset of labor and decreasing the rate of cesarean delivery (assuming vaginal breech delivery is not desired). ECV has been proven to have a high degree of safety and success at this gestational age, but can be initiated earlier (34 to 35 weeks) to improve the success rate. Earlier ECV will probably reduce the cesarean delivery rate, but the safety of ECV performed before 36 weeks is less well-established.

ECV is also appropriate for a transverse or oblique presentation. (See "External cephalic version".)

36 to 41 weeks of gestation

Screen for group B beta-hemolytic streptococcus — In the United States, all pregnant women are screened at 36+0 to 37+6 weeks of gestation for group B beta-hemolytic streptococcus (GBS) colonization with swabs of both the lower vagina and rectum. The only patients who are excluded are those with GBS bacteriuria earlier in the current pregnancy or those who gave birth to a previous infant with invasive GBS disease as these women should receive intrapartum antibiotic prophylaxis. Intrapartum chemoprophylaxis of colonized women has been proven to reduce the incidence of early-onset neonatal GBS. (See "Early-onset neonatal group B streptococcal disease: Prevention".)

Patient education in preparation for labor and delivery

●Management of labor pain:

•(See "Preparation for childbirth".)

•(See "Continuous labor support by a doula".)

•(See "Nonpharmacologic approaches to management of labor pain".)

•(See "Pharmacologic management of pain during labor and delivery".)

●Route of delivery – (See "Cesarean birth on maternal request" and "Choosing the route of delivery after cesarean birth".)

●Induction of labor – (See "Induction of labor with oxytocin" and "Induction of labor: Techniques for preinduction cervical ripening".)

●Postterm pregnancy – If the cervix is partially dilated and the patient desires an intervention, membrane stripping/sweeping after 39 weeks may hasten the onset of labor. (See "Induction of labor with oxytocin", section on 'Membrane stripping'.)

For women ≥41 weeks of gestation, we suggest induction rather than expectant management. (See "Postterm pregnancy".)

Patient education regarding postpartum issues

●Postpartum contraception – (See "Postpartum contraception: Counseling and methods".)

●Postpartum care and complications – (See "Overview of the postpartum period: Normal physiology and routine maternal care" and "Overview of the postpartum period: Disorders and complications".)

●Breastfeeding – (See "Breastfeeding: Parental education and support", section on 'Initial clinical assessment and support'.)

●Choosing, and possibly meeting with, a pediatrician [31].

●Neonatal circumcision – (See "Neonatal circumcision: Risks and benefits".)

●Newborn safety and care – (See "Sudden infant death syndrome: Risk factors and risk reduction strategies", section on 'Sleep position and environment'.)

MANAGEMENT OF PREGNANCY COMPLICATIONS — See individual topic reviews on specific pregnancy complications.

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: General prenatal care".)

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Basics topic (see "Patient education: Postpartum depression (The Basics)")

●Beyond the Basics topics (see "Patient education: Avoiding infections in pregnancy (Beyond the Basics)" and "Patient education: Should I have a screening test for Down syndrome during pregnancy? (Beyond the Basics)" and "Patient education: Group B streptococcus and pregnancy (Beyond the Basics)")

SUMMARY AND RECOMMENDATIONS

●Data as to what constitutes the optimal number and frequency of prenatal visits, and the optimal content of those visits, are limited. (See 'Frequency of prenatal visits' above and 'Ongoing assessments' above and 'Periodic assessments and procedures' above.)

●Pregnant women should be assessed at least once during pregnancy or the postpartum period for depression and anxiety symptoms using a validated screening tool. (See 'Depression screening' above.)