What is the recommended schedule and components of a proper prenatal check-up for obstetric (OB) patients?

Prenatal Care Schedule and Components for Obstetric Patients

All pregnant women should receive comprehensive prenatal care beginning in the first trimester, with visit frequency determined by risk stratification: low-risk women require visits every 3-4 weeks until 28 weeks, then every 2 weeks until 36 weeks, then weekly until delivery, while high-risk women need more frequent monitoring starting at 2-3 week intervals from 24-32 weeks, then every 2 weeks until delivery. 1, 2

First Trimester Care (Weeks 1-13)

Initial Visit Laboratory Screening

All pregnant women must undergo comprehensive blood work at the first prenatal visit, including: 2, 3

• Complete blood count to establish baseline hematologic parameters 2
• Blood typing and antibody screening to identify potential blood incompatibilities 2, 3
• Hepatitis B surface antigen (HBsAg) to recognize and reduce mother-to-child transmission risk 2, 3
• HIV antibody testing for all pregnant women 1, 2, 3
• Syphilis serology to detect and treat maternal infection 2, 3
• Rubella antibody status to assess immunity 2, 3
• Cervical cultures and Pap smear at the initial visit 3
• Fasting blood glucose to screen for pre-existing diabetes 3

High-Risk Patient Additional Testing

Women with chronic hypertension require expanded baseline assessment: 3

• Complete blood count
• Liver enzymes
• Renal function tests (serum creatinine)
• Uric acid levels

Women with pre-existing diabetes need: 2, 3

• Hemoglobin A1C
• Thyroid-stimulating hormone
• Serum creatinine
• Urinary albumin-to-creatinine ratio
• Comprehensive eye examination for diabetic retinopathy

First Trimester Aneuploidy Screening (11-14 weeks)

Combined first trimester screening achieves 85-90% detection rate for Down syndrome with 5% false-positive rate, including: 2

• Nuchal translucency ultrasound measurement
• Pregnancy-associated plasma protein A (PAPP-A)
• Free beta-hCG or total hCG

Cell-free DNA screening offers superior performance with 99% detection rate for trisomy 21 and 1-9% screen-positive rate. 2

Early Gestational Diabetes Screening

Women with high-risk characteristics must undergo immediate glucose testing at the first prenatal visit, including those with: 2, 3

• Marked obesity
• Prior gestational diabetes
• Strong family history of diabetes

Second Trimester Care (Weeks 14-27)

Anatomic Survey and Screening (16-20 weeks)

All pregnant women should receive at least one comprehensive ultrasound between 18-20 weeks for: 4

• Fetal biometry to assess appropriate growth
• Detailed fetal anatomic survey
• Placental location and appearance evaluation
• Amniotic fluid assessment

Quadruple Marker Screening (16-18 weeks)

For women who did not undergo first trimester screening, offer quadruple marker test including: 2

• Alpha-fetoprotein (AFP)
• Human chorionic gonadotropin (hCG)
• Unconjugated estriol
• Inhibin A

Maternal serum alpha-fetoprotein screening detects 75-90% of open neural tube defects and 95% of anencephaly cases. 2

Universal Gestational Diabetes Screening (24-28 weeks)

All women not previously diagnosed with diabetes must undergo screening at 24-28 weeks using: 2, 3

• 50-gram glucose challenge test, OR
• Oral glucose tolerance test

Women with negative early testing but high-risk features require retesting at 24-28 weeks. 3

Third Trimester Care (Weeks 28-40+)

Routine Monitoring Components

At every prenatal visit after 20 weeks, assess for signs and symptoms of preeclampsia: 1

• Blood pressure measurement (critical to avoid errors implicated in maternal deaths)
• Urinary protein assessment
• New headache or visual disturbances
• Epigastric pain or vomiting
• Reduced fetal movements or small-for-gestational-age concerns

Visit Frequency by Risk Status

Low-risk multiparous women (no risk factors from Box 2 criteria): 1

• Follow local protocols consistent with NICE guidelines
• Typical schedule: weeks 28,34,36,38,40,41

Women with one predisposing risk factor: 1

• 24-32 weeks: Maximum 3-week intervals between assessments
• 32 weeks to delivery: Maximum 2-week intervals between assessments

Fetal Movement Monitoring (Last 8-10 weeks)

All mothers must be taught to monitor fetal movements during the last 8-10 weeks of pregnancy and report immediately any reduction in perceived movements. 1, 4

When decreased fetal movement is reported, perform: 4

• Nonstress test (NST) to assess immediate fetal oxygenation (reactive = ≥2 accelerations in 20 minutes)
• Amniotic fluid volume assessment with maximum vertical pocket ≥2 cm considered normal
• Full biophysical profile if NST is non-reactive or amniotic fluid abnormal

High-Risk Pregnancy Fetal Surveillance

For high-risk conditions (advanced maternal age, obesity, hypertensive disorders, diabetes, chronic renal disease, thyroid disorders, history of stillbirth, IUGR, multiple gestations), initiate antenatal fetal surveillance at 32-34 weeks' gestation: 4

Weekly or twice-weekly testing has become standard clinical practice, though optimal interval lacks rigorous evidence. 4

Testing modalities include: 4

• Nonstress test (NST) - preferred over oxytocin stress test
• Modified biophysical profile (NST + amniotic fluid volume)
• Full biophysical profile (NST + ultrasound assessment of fetal breathing, body movements, tone, amniotic fluid)
• Umbilical artery Doppler if growth restriction suspected

Gestational Diabetes Mellitus Specific Monitoring

Women with GDM require: 1

• Blood pressure and urinary protein measurement at each visit to detect preeclampsia
• Fetal movement monitoring during last 8-10 weeks
• Fetal ultrasound screening for congenital anomalies if A1C ≥7.0% or fasting glucose ≥120 mg/dl
• Blood glucose monitoring during labor for those treated with insulin or glyburide

Timing of Delivery

For well-controlled GDM, no data support delivery before 38 weeks' gestation in absence of maternal or fetal compromise. 1

Intensify fetal surveillance when pregnancy continues beyond 40 weeks' gestation. 1

Special Populations

HIV-Infected Pregnant Women

HIV-infected women require: 1

• HIV prevention counseling including perinatal transmission risk discussion
• Antiretroviral therapy counseling during pregnancy
• Scheduled cesarean section at 38 weeks to reduce perinatal transmission risk
• Avoidance of breastfeeding in the United States

Post-Bariatric Surgery Patients

Require expanded testing every trimester: 3

• Complete blood count
• Serum ferritin and iron studies
• Vitamin B12
• Every 6 months: prothrombin time/INR and vitamin K1

Critical Caveats and Pitfalls

No antenatal testing method can predict stillbirth related to acute events such as placental abruption or cord accidents, regardless of test frequency. 4

Routine testing in low-risk pregnancies can cause iatrogenic prematurity from false-positive results and should be avoided. 4

A normal test result is highly reassuring, with false negatives (stillbirth within 1 week of normal test) being uncommon. 4

Blood pressure measurement errors have been implicated in maternal deaths - proper technique is critical. 1

Women must be educated that preeclampsia can develop between antenatal assessments and know how to contact healthcare professionals at all times. 1