What is the recommended antenatal care schedule and interventions for pregnant individuals in all three trimesters?

Recommended Antenatal Care Schedule and Interventions Across All Three Trimesters

All pregnant women should initiate antenatal care in the first trimester with comprehensive screening, followed by structured visits throughout pregnancy that include trimester-specific interventions for infectious diseases, fetal surveillance, and risk-based prophylaxis. 1, 2

First Trimester Care (Weeks 1-13)

Initial Visit Timing and Essential Components

• Initiate care as early as possible in the first trimester, ideally before 12 weeks gestation, as early antenatal care visits are associated with optimal maternal and fetal outcomes 1, 3
• Begin folic acid supplementation (400-800 mcg daily) immediately upon pregnancy confirmation, or 5 mg daily for women taking sulfasalazine, those with significant small bowel resections, or active small bowel disease 4, 1
• Add potassium iodide supplementation (150 mcg daily) at the initial visit 1

Comprehensive Laboratory Screening

• Perform HIV testing using opt-out screening for all pregnant women at the first prenatal visit, as this approach achieves higher testing rates than opt-in methods 4
• Conduct syphilis serologic testing (RPR or similar) at the first visit; repeat in the third trimester and at delivery for high-risk populations 4
• Test for hepatitis B surface antigen (HBsAg) at the initial visit; repeat late in pregnancy for women at high risk (injection drug users, those with concurrent STDs) 4, 5
• Screen for gonorrhea and chlamydia at the first visit for women at risk or in high-prevalence areas 4
• Perform blood grouping and Rh typing to identify women requiring Rh immunoglobulin prophylaxis 5

Risk Stratification and Prophylaxis

• Identify women requiring low-dose aspirin (81-150 mg daily) and initiate before 16 weeks gestation for those with major risk factors: previous preeclampsia, chronic hypertension, pregestational diabetes, BMI ≥35, chronic kidney disease, or antiphospholipid syndrome 1, 2, 5
• Measure blood pressure at every visit to identify chronic hypertension and preeclampsia risk factors 5
• For women with pregestational diabetes, establish multidisciplinary care including endocrinologist, maternal-fetal medicine specialist, registered dietitian, and diabetes educator 1

Aneuploidy Screening at 11-14 Weeks

• Perform first-trimester combined screening (nuchal translucency measurement plus biochemical markers) between 11 weeks 4 days and 13 weeks 6 days, achieving detection rates of 85-92% for Down syndrome with false-positive rates of 1-5% 5
• Offer cell-free DNA screening as a more sensitive option where cost permits 5
• For multiple gestations, assess chorionicity and amnionicity, as this determines prognosis and surveillance intensity 4, 5

Second Trimester Care (Weeks 14-27)

Anatomic and Cardiac Surveillance

• Perform detailed fetal anatomy ultrasound between 16-22 weeks gestation to detect congenital anomalies 1, 2
• Schedule fetal echocardiogram between 16-22 weeks for women with pregestational diabetes to detect cardiac anomalies 1, 2

Infectious Disease Screening

• Retest for chlamydia in the third trimester for women at increased risk (age <25 years, new or multiple sex partners) to prevent maternal postnatal complications and neonatal infection 4
• Consider bacterial vaginosis testing early in the second trimester for asymptomatic patients at high risk for preterm labor 4

Continued Prophylaxis

• Continue low-dose aspirin for preeclampsia prophylaxis through 36 weeks gestation 1, 2
• Monitor fasting glucose <95 mg/dL and either 1-hour postprandial <140 mg/dL or 2-hour postprandial <120 mg/dL for women with pregestational diabetes 1

Third Trimester Care (Weeks 28-40)

Infectious Disease Rescreening

• Repeat HIV testing in the third trimester (before 36 weeks) for women in states with elevated HIV incidence, facilities with prenatal screening prevalence ≥1 per 1000, or women at high risk for acquiring HIV 4
• Repeat syphilis testing in the third trimester for high-risk women 4
• Retest hepatitis B surface antigen for women who were negative initially but remain at high risk 4

Fetal Surveillance

• Initiate antepartum fetal surveillance at 32-34 weeks gestation for high-risk pregnancies, including those with pregestational diabetes, fetal growth restriction, or other complications 2
• Perform weekly cardiotocography (CTG) testing after viability for fetal growth restriction without absent/reversed end-diastolic velocity 4
• Conduct ultrasound for fetal growth assessment, especially for women with risk factors 2

Preeclampsia Monitoring

• Screen for preeclampsia signs at every visit after 20 weeks: new hypertension, proteinuria, headache, visual disturbances, epigastric pain, and reduced fetal movements 1
• Observe more stringent social distancing after 28 weeks during pandemic situations 2

Immunizations

• Administer Tdap vaccination between 27-36 weeks gestation to ensure optimal transplacental antibody transfer for neonatal pertussis protection 5

Venous Thromboembolism Prophylaxis

• Provide VTE prophylaxis during the third trimester for outpatients with active inflammatory bowel disease, unless contraindicated 4
• Assess VTE risk for all pregnant women; consider antepartum antithrombotic prophylaxis for those with hereditary thrombophilia and family history of VTE 2

Delivery Planning

• For women with good glycemic control and no vascular complications, plan delivery at 39 0/7 to 39 6/7 weeks gestation 2
• For women with poor glycemic control, vascular complications, or prior stillbirth, consider delivery at 36 0/7 to 38 6/7 weeks 2
• Discontinue aspirin at 36 weeks gestation 1

Special Populations Requiring Enhanced Surveillance

Multiple Gestations

• Monochorionic twins require more frequent follow-up than dichorionic twins due to 10% overall mortality rate from complications like twin-twin transfusion syndrome 4
• Perform weekly umbilical artery Doppler evaluation for severe fetal growth restriction (estimated fetal weight <3rd percentile) 4

Inflammatory Bowel Disease

• Assess IBD patients at least once in a consultant-led obstetric clinic; joint IBD antenatal clinics may offer optimal care 4
• Screen for mental health issues before, during, and after pregnancy, with onward referral to appropriate services 4
• Continue advanced therapies (vedolizumab, ustekinumab) throughout pregnancy to minimize relapse risk, as continuation is not associated with adverse maternal or fetal outcomes 4

HIV-Positive Women

• Monitor CD4+ counts and HIV-1 RNA levels approximately every trimester (every 3-4 months) to determine need for antiretroviral therapy adjustments 4
• For women with unknown HIV status at labor and delivery, perform rapid testing promptly to allow for intrapartum and neonatal antiretroviral prophylaxis 4

Mental Health Screening Throughout Pregnancy

• Inquire about mental health at every consultation and connect women to relevant resources such as counseling or support groups 1, 2
• Given the increased burden of mental health disease in people with IBD, perform mental health screening with onward referral before, during, and after pregnancy 4

Lifestyle and Nutritional Counseling

• Promote balanced nutrition with "five-a-day" (2 servings fruit, 3 servings vegetables) 1
• Recommend regular moderate exercise such as brisk walking, swimming, or prenatal yoga appropriate for pregnancy 1
• Counsel on complete avoidance of alcohol, tobacco, and recreational drugs 1

Common Pitfalls to Avoid

• Do not delay HIV testing or use opt-in approaches that require extensive pretest counseling, as these reduce testing rates 4
• Avoid performing nuchal translucency measurements outside the 11 weeks 4 days to 13 weeks 6 days window, as accuracy decreases 5
• Do not administer Tdap vaccination at 12 weeks; wait until 27-36 weeks for optimal neonatal antibody transfer 5
• Avoid gadolinium-enhanced MRI during pregnancy, as it is relatively contraindicated with no established indications for fetal evaluation 4
• Do not continue methotrexate, JAK inhibitors, sphingosine-1-P modulators, tofacitinib, filgotinib, upadacitinib, ozanimod, or etrasimod during pregnancy due to teratogenicity risk 4