Prenatal care: Second and third trimesters

INTRODUCTION — The goal of prenatal care is the birth of a healthy child with minimal risk for the mother. After the initial prenatal visit, it consists of ongoing evaluation of the health status of both the mother and fetus, counseling about pre- and postpartum issues, and anticipation of problems with intervention, if possible, to prevent or minimize morbidity. Thus, prenatal care represents a series of assessments, discussions, and interventions over time that are often applied by different health care providers. As a result, the quality of prenatal care and the effect of individual components on outcome are difficult to measure.

This topic will discuss prenatal care in the second and third trimesters. Other important issues related to prenatal care are reviewed separately:

●Prenatal care issues at the first visit and in the first trimester: (See "Prenatal care: Initial assessment".)

●Specific issues related to prenatal care for patients with multiple gestations: (See "Twin pregnancy: Overview" and "Triplet pregnancy".)

●Prenatal care during the COVID-19 pandemic: (See "COVID-19: Overview of pregnancy issues", section on 'Prenatal care'.)

●Diagnosis and management of pregnancy complications: See individual topic reviews on specific pregnancy complications.

GENERAL PRINCIPLES

Respectful, equitable, and supportive maternity care — Respectful, equitable, and supportive maternity care maintains dignity, privacy, and confidentiality; ensures freedom from harm and mistreatment; and enables informed choice and continuous support during labor and childbirth [1-3]. It requires open, transparent, and empathetic communication aligned with the patient's health literacy, culture, language, and accessibility needs [4]. Multiple organizations have developed tools to evaluate the delivery of maternity care and recommendations to ensure that it is respectful, equitable, and supportive [5-8]. (See "Racial and ethnic inequities in obstetric and gynecologic care and role of implicit biases", section on 'Strategies to reduce health care inequities'.)

In the United States, 90 percent of 2400 respondents to an online survey were satisfied with the care they received during pregnancy, but 20 percent overall reported mistreatment (eg, ignored by health care provider, requests for help refused, or not responded to; violation of physical privacy; verbal abuse) during maternity care [9]. Approximately 45 percent of all respondents reported holding back from asking questions or discussing concerns with their providers, often because they or someone else thought what they were feeling was normal, they felt embarrassed, or they worried that their maternity care provider might think they were being difficult. Approximately 30 percent of all respondents and 40 percent of Black, Hispanic, and multiracial respondents reported discrimination during maternity care.

Definition of high- versus low-risk pregnancy — There is no standard definition of a high- versus low-risk pregnancy.

●A high-risk pregnancy is a broad term that encompasses patients with a medical or surgical conditions, past or current obstetric problems, or social or demographic factors that increase the risk for an adverse maternal, fetal, or newborn outcome or a complicated birth; however, there is no precise definition.

●A low-risk or average-risk pregnancy generally refers to a singleton gestation without factors that increase the risk for an adverse maternal, fetal, or newborn outcome or a complicated birth.

Frequency of prenatal visits — Observational data suggest that prenatal care saves maternal, fetal, and newborn lives and that an association exists between the number of prenatal visits and/or early gestational age at the initiation of care and pregnancy outcome, after controlling for confounding factors (eg, length of gestation, personal characteristics [socioeconomic and migrant status]) [10,11]. However, data as to what constitutes the optimal number and frequency of prenatal visits or the optimal content of those visits are limited. A 2022 Agency for Healthcare Research and Quality (AHRQ) review of comparative studies from high-income countries evaluating a wide range of reduced and traditional visit schedules for routine antenatal care found moderate-level evidence of a lack of differences for gestational age at birth and frequency of small for gestational age newborns, neonatal intensive care unit (NICU) admissions, and low Apgar score [12]. They also found low-level evidence of a lack of differences in maternal anxiety or frequency of preterm birth and low birth weight. A 2023 meta-analysis comparing a reduced number of routine antenatal visits (6 to 10) with a standard schedule (12 to 15) reported similar findings [13]. New studies are needed to evaluate other outcomes, including patient experience measures and potential differential effects among different populations or settings.

●United States – In the United States, the typical intervals for prenatal visits for nulliparous patients with low-risk pregnancies are every 4 weeks until 28 weeks of gestation, every 2 weeks from 28 to 36 weeks, and then weekly until delivery [14]. According to this schedule, a patient with a low-risk pregnancy whose first visit is at six weeks of gestation and whose last visit is at 39 weeks will have 14 prenatal visits. Individualization of prenatal visit schedules is reasonable [15]. Patients with high-risk pregnancies, including high-risk psychosocial conditions, are seen more frequently, depending on the nature of their high-risk condition, whereas parous patients with low-risk pregnancies may be seen less frequently.

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

•In randomized trials of high-risk pregnancies assigned to routine versus enhanced prenatal care (eg, extra office visits, health education, home visits, telephone contact, psychosocial support), enhanced care did not improve pregnancy outcome [16-18].

•In a retrospective cohort study of over 7200 consecutive uncomplicated term births, patients who had >10 versus ≤10 prenatal visits had similar outcomes (NICU admission, five-minute Apgar score <7, neonatal demise, small for gestational age newborn) [19]. However, the high-utilization group was 33 percent more likely to undergo induction of labor and 50 percent more likely to have a cesarean birth than the low-utilization group. The reason for this relationship was unclear.

●National Institute of Health and Clinical Excellence (NICE) – NICE guidelines suggest a total of 11 prenatal care appointments over 39 weeks for nulliparous patients and 9 appointments for parous patients (including the initial booking appointment); the specific purpose/goal for each prenatal visit is also described [20]. This approach accounts for the cost and time constraints of contemporary society and the lack of proven efficacy of frequent prenatal visits in randomized trials.

●World Health Organization (WHO) – The WHO global antenatal care guidelines suggest a minimum of eight antenatal visits (one in the first trimester, two in the second trimester, and five in the third trimester) for all patients, regardless of parity [21]. 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 patients with low-risk pregnancies in middle- and lower-income countries who had reduced antenatal visits (typically fewer than five visits) compared with more visits (relative risk [RR] 1.15, 95% CI 1.01-1.32) [11]. The review also noted that patients in all income settings were less satisfied with the reduced visits schedule.

●Europe – A survey of members of national societies in 26 mostly European countries found that most patients booked their first prenatal appointment in the first trimester and the number of visits for routine antenatal care generally ranged from 6 to 10, although a few countries offered fewer than six visits to multiparous patients and a few offered more than 10 visits for both nulliparous and multiparous patients [22].

Telehealth — The COVID-19 pandemic showed that telehealth (telemedicine or televisits) and use of home devices could be safely and effectively integrated into routine prenatal care and was acceptable to patients [23-27]. Telehealth supplements in-person office visits and has been particularly useful for patients with perinatal mood disorders, diabetes, or hypertension. A rapid review concluded that replacing or supplementing in-person maternal care with telehealth care generally resulted in similar, and sometimes better, clinical outcomes and patient satisfaction, but the effect on access to care, health equity, and harms was unclear [27]. A meta-analysis of telehealth compared with in-person antenatal care found that studies did not report negative effects from incorporating televisits into prenatal care and patients preferred replacing some in-person visits with televisits, but the evidence base was generally limited and insufficient to allow clear conclusions about most outcomes and the optimum hybrid system [28].

Signs and symptoms that should be reported to the health care provider — Pregnant patients should be counseled about signs and symptoms that need to be reported promptly to their health care provider. These include, but are not limited to:

●Vaginal bleeding – (See "Evaluation and differential diagnosis of vaginal bleeding before 20 weeks of gestation".)

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

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

●Abdominal pain, which has several possible obstetric, gynecologic, medical, and surgical causes. (See "Approach to acute abdominal/pelvic pain in pregnant and postpartum patients".)

●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, new or worsening hypertension [if home blood pressure monitoring is being performed]). (See "Preeclampsia: Clinical features and diagnosis".)

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

Mental health screening — Patients should be screened for depression and anxiety at the initial prenatal visit, later in pregnancy, and at postpartum visits using a standardized, validated tool, such as one of these examples (table 1 and figure 1A-B and table 2) [29]. There is no consensus as to the optimal time to perform screening between the initial prenatal visit screen and the postpartum screen.

Systems should be in place to ensure timely access to assessment and diagnosis, effective treatment, and appropriate monitoring and follow-up based on severity [30].

Screening for bipolar disorder (table 3) should be performed before initiating pharmacotherapy for anxiety or depression because misdiagnosis can lead to inappropriate treatment, which may precipitate mania, mixed states, rapid cycling, or psychosis.

Routine ongoing assessments — The following routine assessments are performed at each prenatal visit. These simple, noninvasive, inexpensive assessments detect 20 to 50 percent of fetuses with growth abnormality, prevent 70 percent of eclampsia by early detection of preeclampsia, and identify 80 percent of breech presentations prior to labor when external cephalic version (ECV) can be performed to decrease the need for cesarean birth [31-36]. Ongoing assessment of gestational weight gain combined with behavioral counseling interventions aimed at promoting healthy weight gain and preventing excess gestational weight gain have a moderate net benefit for pregnant persons [37].

●History

•Assess maternal perception of fetal activity.

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

•Assess significant events since the prior visit, such as medical or surgical illness, stressors, travel outside of the country, or exposure to infection (eg, Zika virus, severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2], cytomegalovirus, parvovirus B19, varicella zoster, rubella, syphilis, herpes simplex virus, HIV, toxoplasmosis, tuberculosis, malaria). See individual topic reviews on each infectious disease.

●Physical and laboratory examination

•Measure blood pressure – The procedure for checking blood pressure is generally similar to that in nonpregnant patients (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 (figure 2) in normal pregnancies (ie, those with no chronic hypertension, preeclampsia, or diabetes and with birth of an appropriate size for gestational age newborn at term). (See "Maternal adaptations to pregnancy: Cardiovascular and hemodynamic changes", section on 'Changes in systemic hemodynamics'.)

During pregnancy, hypertension is defined as a systolic blood pressure ≥140 mmHg and/or diastolic blood pressure ≥90 mmHg. The definitions for the various hypertensive disorders of pregnancy are described in the table (table 4).

In patients at increased risk for preeclampsia, an expert working group suggested monitoring blood pressure in the office and/or at home every two weeks until 20 weeks, and weekly thereafter, with more frequent determinations if warranted by the clinical condition [38]. In patients at high risk for developing new or worsening hypertension, self-monitoring of blood pressure is equivalent to routine office-based monitoring for diagnosis and no more effective than routine office-based blood pressure monitoring for reducing the development of severe hypertension or preeclampsia [39,40]. However, it is convenient for patients and helps to identify white coat hypertension and avoid escalation of evaluation and therapy in these patients.

Although measurement of blood pressure is necessary for diagnosis of hypertension, no early pregnancy mean arterial pressure, systolic blood pressure, or diastolic blood pressure threshold performs well for predicting future development of preeclampsia or gestational hypertension. In a systematic review, blood pressure ≥140/90 mmHg before 20 weeks was a good predictor of preeclampsia occurrence (positive likelihood ratio 5.95 versus <3 for 120/80 and 130/80), but blood pressures <120/80 mmHg, <130/80 mmHg, and <140/90 mmHg were not predictive of absence of preeclampsia occurrence (negative likelihood ratio >0.2) [41]. In another systematic review, a hypertensive disorder of pregnancy developed in 11.6 percent of patients with blood pressures of 120-139/80-89 mmHg and 5.6 percent of those with blood pressures lower than 120/80 mmHg before 20 weeks of gestation [42].

•Measure weight – Weight gain target ranges depend on the patient's baseline body mass index (table 5). Low or high gestational weight gain can impact pregnancy outcome. (See "Gestational weight gain".)

•Document the fetal heart rate – The normal baseline fetal heart rate is 110 to 160 beats per minute.

•Dipstick the urine to check for protein, although the value of this test is questionable in patients with normal blood pressure [31,43-45].

•Assess fetal growth in the second and third trimesters by abdominal examination and measurement of fundal height. Ultrasound assessment is generally reserved for patients with risk factors for fetal growth restriction or growth acceleration, but some clinicians obtain a third trimester ultrasound examination to monitor fetal growth routinely. (See 'Screen for fetal growth restriction' below and "Fetal macrosomia", section on 'Patients with diabetes'.)

•Determine fetal presentation in the third trimester.

PERIODIC ASSESSMENTS AND PROCEDURES — Prenatal screening should be performed early within the recommended intervals to allow adequate time for counseling about test results, performing diagnostic tests if indicated, and discussing management options, including in utero therapeutic procedures if available, pregnancy termination if the patient chooses this option, and how findings may affect the preferred site of birth. Clinicians and patients should be aware of local regulations regarding both discussion of and availability of pregnancy termination.

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'). However, if the patient initially presents for prenatal care in the second or third trimester, non-time-sensitive tests are performed at that time.

15 to 24 weeks of gestation

Screen for short cervix by transvaginal ultrasound — 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 at the time of the ultrasound examination screening for fetal anomalies, usually around 18 to 22 weeks. In patients with a short cervix, interventions such as treatment with vaginal progesterone or cerclage have reduced the rate of subsequent preterm birth. Screening, diagnosis, and management of short cervix are discussed in detail separately. (See "Short cervix before 24 weeks: Screening and management in singleton pregnancies".)

Offer screening for neural tube defects — For patients who choose to undergo screening for neural tube defects, ultrasound examination and maternal serum alpha-fetoprotein (MSAFP) and are both effective methods. Ultrasound examination is generally the preferred approach. It is performed as part of fetal anatomy survey at 18 to 22 weeks. MSAFP is performed ideally at 16 to 18 weeks of gestation but can be performed as early as 15 weeks or as late as 22 weeks. In utero therapy may be an option for patients with myelomeningocele. (See "Neural tube defects: Overview of prenatal screening, evaluation, and pregnancy management".)

Offer screening or diagnostic testing for trisomy 21 and other genetic disorders — We believe that all pregnant people should be offered prenatal assessment for aneuploidy by a screening test or by diagnostic testing regardless of maternal age or other risk factors, in agreement with American College of Obstetricians and Gynecologists (ACOG) guidelines [46]. For patients who book their first prenatal appointment in the second trimester, the quadruple test (Quad test; ie, alpha-fetoprotein [AFP], unconjugated estriol [uE3], human chorionic gonadotropin [hCG], and inhibin A) is one option for screening; maternal blood is drawn between 15 and 22 weeks of gestation for this test, which is performed on serum. Cell-free DNA screening of maternal blood is another option for screening and its use is more common than the Quad test in many practices because of its higher sensitivity and specificity. Other fetal genetic abnormalities may be detected in the course of screening and diagnosis of Down syndrome (see "Down syndrome: Overview of prenatal screening"). Amniocentesis is performed for diagnostic testing. (See "Down syndrome: Overview of prenatal screening", section on 'Diagnostic testing'.)

In the United States, genetic carrier screening for cystic fibrosis and spinal muscular atrophy is routinely offered, and red cell indices are routinely used to screen for carriers of hemoglobinopathies [47]. For other heritable disorders, clinicians may choose to take an ethnic-specific or panethnic approach. Alternatively, clinicians may offer all patients an expanded carrier screening panel. These issues are discussed in more detail separately as screening and diagnostic testing are typically discussed at the first prenatal visit, which is ideally in the first trimester. (See "Prenatal care: Initial assessment", section on 'Aneuploidy screening and diagnosis' and "Prenatal care: Initial assessment", section on 'Carrier screening'.)

Offer screening for fetal anomalies — For patients who choose to undergo ultrasound screening for structural fetal anatomic anomalies, the procedure is optimally performed in the second trimester, between 18 and 22 weeks of gestation. Although many congenital anomalies can be identified by ultrasound in the first trimester, sensitivity is higher in the second trimester. Additional and follow-up testing may be needed to confirm the suspected diagnosis. (See "Overview of ultrasound examination in obstetrics and gynecology", section on 'Utility of routine examination'.)

24 to 28 weeks of gestation

Screen for gestational diabetes — In the United States and several other countries, universal screening for gestational diabetes is performed at 24 to 28 weeks of gestation. Some countries use a selective (risk factor-based) screening approach at 24 to 28 weeks rather than universal screening, but it is less effective. The screening test used varies worldwide (table 6A-B). (See "Gestational diabetes mellitus: Screening, diagnosis, and prevention", section on 'One- and two-step approaches'.)

Patients with significant risk factors for diabetes (eg, gestational diabetes in a prior pregnancy) may be screened early in pregnancy for undiagnosed overt diabetes; those with normal test results should be screened again at 24 to 28 weeks. (See "Gestational diabetes mellitus: Screening, diagnosis, and prevention", section on 'Screening for overt diabetes in early pregnancy'.)

Screen for red blood cell antibodies and administer anti-D immune globulin to D-negative patients

●In D-negative patients, red blood cell (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 D-positive patients who had a negative RBC antibody screen early in pregnancy, rescreening for RBC antibodies at 28 weeks 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, defined as follows based on data derived from an iron-supplemented population [48]:

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

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

Anemic patients should be tested for iron deficiency; some providers check for iron deficiency in all patients because of the high prevalence in pregnancy. Iron deficiency anemia, which is common, can usually be corrected before delivery by appropriate oral or parenteral supplementation. Prevalence, evaluation, and treatment of iron deficiency and anemia are reviewed separately. (See "Anemia in pregnancy".)

28 to 36 weeks of gestation

Screen for sexually transmitted infections — In patients at increased risk of acquiring a sexually transmitted infection (STI) (table 7), in the United States, the Centers for Disease Control and Prevention (CDC) recommend testing for HIV, syphilis, chlamydia, and gonorrhea in the third trimester (28 to 36 weeks) [49].

●HIV – The test for HIV is ideally performed with a combination antigen/antibody immunoassay, which requires a blood draw. At the point-of-care, other options for testing can be performed on oral secretions or finger stick samples. (See "Screening and diagnostic testing for HIV infection", section on 'Tests'.)

●Syphilis – Testing for syphilis requires a blood sample for either a nontreponemal or treponemal test. (See "Syphilis: Screening and diagnostic testing", section on 'Serologic tests'.)

●C. trachomatis – Testing is performed with a nucleic acid amplification test (NAAT) on a vaginal (preferred), urethral, endocervical, or rectal swab or on urine. (See "Clinical manifestations and diagnosis of Chlamydia trachomatis infections", section on 'Nucleic acid amplification testing (test of choice)'.)

●N. gonorrhoeae – Testing is performed with NAAT on a vaginal swab (preferred), urethral, endocervical, rectal, or oropharyngeal swab or urine. (See "Clinical manifestations and diagnosis of Neisseria gonorrhoeae infection in adults and adolescents", section on 'Asymptomatic patients'.)

The value of repeat chlamydia and gonorrhea testing in individuals at high risk is supported by a retrospective study of STI test results in 1.3 million pregnant individuals in the United States [50]:

●Among patients who tested positive for chlamydia or gonorrhea at least once during pregnancy and were retested before giving birth, the last test was positive in 6 percent (969 out of 16,039) of those positive for chlamydia and 3.8 percent (100 out of 2610) of those positive for gonorrhea earlier in pregnancy.

●Among patients 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 out of 50,959) had a subsequent positive test for chlamydia and 1.1 percent (564 out of 51,077) had a subsequent positive test for gonorrhea.

In some areas, repeat syphilis and HIV testing in the third trimester is mandatory for all patients. Routinely retesting all patients for syphilis in the third trimester was cost-effective in some modeling studies, but not in others [51-53] (see "Syphilis in pregnancy"). Third-trimester HIV testing may be cost-effective for all pregnant individuals [54]. Where third-trimester HIV retesting is not mandatory, rescreening using an opt-out approach is recommended for patients at increased risk for acquiring HIV infection, patients residing in or receiving care in areas of high HIV prevalence, incarcerated patients, and patients who declined testing earlier in pregnancy [49,55]. The basis of this recommendation is that appropriate intervention peripartum can significantly reduce perinatal HIV 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 individuals with HIV in resource-rich settings" and "Screening and diagnostic testing for HIV infection".)

Screen for fetal growth restriction — Ongoing assessment of fetal growth by maternal physical examination (fundal height measurements) is a routine component of prenatal care. Sonographic assessment of fetal growth is indicated in the third trimester for those pregnancies at high risk of fetal growth restriction (algorithm 1). Although early identification of growth-restricted fetuses allows for closer surveillance and earlier intervention in case of fetal decompensation, the use of ultrasound in the third trimester to screen for fetal growth disturbance in low-risk pregnancies has not been proven to be effective for reliably detecting these fetuses or improving outcome. These data are reviewed separately. (See "Fetal growth restriction: Screening and diagnosis", section on 'Screening' and "Fetal growth restriction: Evaluation".)

Determine the appropriate approach for antenatal fetal surveillance — All pregnant individuals should be aware of fetal movement, either subjectively or by using a quantitative method (kick counts), and they should 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, or a combination of both tests, is indicated in pregnancies where the risk of antepartum fetal demise is increased, which ACOG has defined as a stillbirth rate greater than 0.8 per 1000 and associated with a relative risk (RR) or odds ratio for stillbirth >2.0 compared with pregnancies without the condition [56]. This is the false-negative rate of a biophysical profile or modified biophysical profile. These conditions include but are not limited to fetal growth restriction, hypertensive disorders, pregestational diabetes or gestational diabetes treated with medication, sickle cell disease, renal insufficiency, multiple gestation, and systemic lupus erythematosus. (See "Overview of antepartum fetal assessment", section on 'Indications for fetal assessment'.)

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.

Vaccination — Third-trimester maternal vaccination reduces the chances of maternal infection to the target infections and subsequent infant exposure. It also provides passive protection to infants exposed to the target infections in the first few months of life.

●Vaccination with the adjuvanted tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) is recommended during each pregnancy, ideally between 27 and 36 weeks of gestation. (See "Immunizations during pregnancy", section on 'Tetanus, diphtheria, and pertussis vaccination'.)

●Protecting the infant against respiratory syncytial virus (RSV) infection is recommended. For patients who choose to be vaccinated, a single dose of the RSVpreF vaccine is administered to those between 32+0 and 36+6 weeks of gestation during RSV season (September through January in continental United States) [57]. Some informed patients may reasonably choose to forego RSV vaccination during pregnancy and instead plan on postnatal administration of nirsevimab to the infant. Insurance coverage of one approach versus the other may be a factor in decision-making. These issues are discussed in detail separately. (See "Immunizations during pregnancy", section on 'Respiratory syncytial virus'.)

36 to 41 weeks of gestation

Offer external cephalic version of noncephalic fetal presentations — For pregnancies with noncephalic presentations (breech, transverse, oblique), external cephalic version (ECV) is typically performed at 36+0 to 37+0 weeks of gestation. ECV is a safe and effective technique for increasing the chance of cephalic presentation at onset of labor and decreasing the chance of cesarean birth (assuming vaginal breech delivery is not desired). (See "External cephalic version".)

Screen for group B beta-hemolytic streptococcus — In the United States, pregnancies are routinely 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. Exceptions include patients who had GBS bacteriuria earlier in the current pregnancy or those who gave birth to a previous neonate with invasive GBS disease, as these patients should receive intrapartum antibiotic prophylaxis. Patients screened because of preterm labor or preterm prelabor rupture of membranes do not need to be rescreened at 36+0 to 37+6 weeks unless more than five weeks have elapsed since they were screened. Intrapartum antibiotic prophylaxis of colonized patients has been proven to reduce the incidence of early-onset neonatal GBS. (See "Prevention of early-onset group B streptococcal disease in neonates".)

Screen for accelerated fetal growth — Accelerated fetal growth may result in a large for gestational age or macrosomic newborn. Ultrasound examination at term is indicated in patients at risk for macrosomia because of diabetes or clinical suspicion (especially a previous macrosomic newborn) since cesarean birth to reduce the risk of shoulder dystocia is suggested for an estimated fetal weight >4500 g in patients with diabetes and >5000 g in patients without diabetes. (See "Fetal macrosomia", section on 'Risk factors' and "Shoulder dystocia: Risk factors and planning birth of high-risk pregnancies".)

Patient education in preparation for labor and birth

●Management of labor pain: Patients need accurate, unbiased information to enable them to make a plan for labor pain relief that reflects their values and preferences and is flexible [58]. Such information reduces anxiety and leads to a more positive childbirth experience.

•(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 birth – (See "Cesarean birth on patient 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".)

●Post-term pregnancy – Induction is generally suggested for patients who have not given birth by 41+0 weeks of gestation. (See "Postterm pregnancy".)

If the patient desires an intervention to minimize the chances of post-term pregnancy, membrane stripping/sweeping (if the cervix is partially dilated) at office visits at ≥39 weeks may hasten the onset of labor (see "Induction of labor with oxytocin", section on 'Membrane stripping'). Induction of labor at ≥39 weeks is another option. (See "Induction of labor with oxytocin", section on 'At 39 weeks'.)

Patient education regarding postpartum issues

●Postpartum contraception – (See "Contraception: Postpartum 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 [59].

●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'.)

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: Depression during and after pregnancy (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

●Number and content of prenatal visits – Data as to what constitutes the optimal number and frequency of prenatal visits, and the optimal content of those visits, are limited. For patients with low-risk pregnancies, we follow the typical prenatal visit schedule in the United States of every 4 weeks until 28 weeks of gestation, every 2 weeks from 28 to 36 weeks, and then weekly until birth. (See 'Frequency of prenatal visits' above and 'Routine ongoing assessments' above and 'Periodic assessments and procedures' above.)

●Alarm signs and symptoms – Pregnant patients should be counseled about signs and symptoms that should be reported to their health care provider promptly because of potential serious maternal or fetal consequences. These include, but are not limited to (see 'Signs and symptoms that should be reported to the health care provider' above):

•Vaginal bleeding

•Leakage of fluid per vagina

•Decreased fetal activity

•Signs and symptoms of preterm labor

•Signs and symptoms of preeclampsia

•Signs and symptoms suggestive of a medical or surgical disorder

●Ongoing assessments during prenatal care include (see 'Routine ongoing assessments' above):

•Measure blood pressure at every visit

•Measure gestational weight gain at every visit (table 5)

•Review of signs and symptoms of potential pregnancy problems at every visit

•Document fetal heart rate at every visit

•Assess maternal perception of fetal activity at every visit

•Assess fetal growth either through measuring fundal height at every visit and/or by periodic ultrasound evaluation in pregnancies with risk factors for growth restriction

•Determine fetal presentation (starting at ≥34 weeks to discuss external cephalic version [ECV] and route of birth if breech)

•Assess for significant events since the prior visit, such as recent travel, illness, stressors, or exposure to infection (eg, Zika virus, severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2]), sexually transmitted infection [STI])

●Periodic assessments

•Patients should be screened for depression and anxiety during pregnancy (in addition to screening at the first prenatal visit) using a standardized, validated tool (table 1 and figure 1A-B and table 2). (See 'Mental health screening' above.)

•15 to 24 weeks

-Offer gestational age-appropriate screening for neural tube defects and other congenital anomalies. Screening/diagnosis of trisomy 21 and other aneuploidies and carrier screening are offered if not previously offered at an initial first trimester prenatal visit. (See 'Offer screening for neural tube defects' above and 'Offer screening or diagnostic testing for trisomy 21 and other genetic disorders' above and 'Offer screening for fetal anomalies' above.)

-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 an 18 to 22 week 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, but it is commonly performed in pregnancies at high risk for spontaneous preterm birth. (See 'Screen for short cervix by transvaginal ultrasound' above.)

•24 to 28 weeks

-Screen for gestational diabetes (table 6A) and anemia at 24 to 28 weeks of gestation. (See 'Screen for gestational diabetes' above and 'Screen for anemia' above.)

-In D-negative patients, perform red blood cell (RBC) antibody screening at 28 weeks of gestation and administer anti-D immune globulin. (See 'Screen for red blood cell antibodies and administer anti-D immune globulin to D-negative patients' above.)

•28 to 36 weeks

-Screen for STIs in patients at increased risk (table 7). (See 'Screen for sexually transmitted infections' above.)

-Sonographic assessment of fetal growth is indicated in those pregnancies at high risk of fetal growth restriction (algorithm 1). (See 'Screen for fetal growth restriction' above.)

-Perform antenatal fetal testing in pregnancies in which the risk of antepartum fetal demise is increased (eg, fetal growth restriction, hypertensive disorders, pregestational diabetes or gestational diabetes treated with medication, sickle cell disease, renal insufficiency, multiple gestation, systemic lupus erythematosus). It is usually initiated at or after 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 'Determine the appropriate approach for antenatal fetal surveillance' above.)

-Offer ECV at 36 weeks of gestation if the fetus is noncephalic. (See 'Offer external cephalic version of noncephalic fetal presentations' above.)

-Screen for rectovaginal group B beta-hemolytic streptococcus (GBS) colonization at 36+0 to 37+6 weeks of gestation. (See 'Screen for group B beta-hemolytic streptococcus' above.) 

-Work with the patient to prepare for labor, birth, and the postpartum period. (See 'Patient education in preparation for labor and birth' above and 'Patient education regarding postpartum issues' above.)

●Vaccinations against pertussis and respiratory syncytial virus (RSV) are administered in the third trimester (table 8). Evidence for this recommendation is available separately. (See "Immunizations during pregnancy", section on 'Tetanus, diphtheria, and pertussis vaccination' and "Immunizations during pregnancy", section on 'Respiratory syncytial virus'.)