What is the typical prenatal schedule from start of pregnancy to delivery, including ultrasound scans and blood work?

Prenatal Care Schedule from Start of Pregnancy to Delivery

For uncomplicated, low-risk pregnancies, attend prenatal visits monthly until 28 weeks' gestation, then every 2 weeks until 36 weeks, followed by weekly visits until delivery, with a standard anatomy ultrasound at 18-20 weeks and gestational diabetes screening at 24-28 weeks. 1

Standard Visit Schedule

First and Second Trimester (Up to 28 weeks)

• Monthly visits from initial presentation through 28 weeks' gestation to monitor maternal health, screen for complications, and assess fetal growth 1
• First prenatal visit should ideally occur in the first trimester, though office-based scheduling practices vary widely (ranging from 4 to 10.6 weeks) 2

Third Trimester (28-36 weeks)

• Biweekly visits from 28 to 36 weeks' gestation to increase surveillance as pregnancy advances and risks of complications rise 1

Late Third Trimester (36 weeks to delivery)

• Weekly visits from 36 weeks until delivery to monitor for signs of labor, assess fetal well-being, and detect late-developing complications 1

Ultrasound Schedule

Standard Ultrasound Examinations

• Anatomy scan at 18-20 weeks is the minimum recommended ultrasound for all pregnant women to evaluate fetal structure and development 3
• No routine third-trimester ultrasound is recommended for low-risk pregnancies, as it has not shown evidence of improved outcomes 3

Additional Ultrasounds for Specific Indications

• First trimester dating scan if uncertain dates or to confirm viability 3
• Third-trimester growth scan only if specific findings warrant follow-up (such as isolated echogenic bowel, single umbilical artery, or shortened long bones) 3

Blood Work Schedule

Early Pregnancy (First Visit and First Trimester)

• Complete blood count (hemoglobin) at initial visit 4
• Blood type and antibody screen at initial visit 4
• Early gestational diabetes screening at 12-14 weeks for women with BMI ≥30 kg/m² or prior gestational diabetes 1

Mid-Pregnancy (24-28 weeks)

• Universal gestational diabetes screening at 24-28 weeks for all women not previously diagnosed 1
• Repeat complete blood count to assess for anemia 4

Late Second/Early Third Trimester (28 and 34 weeks minimum)

• Hemoglobin, platelet count, liver transaminases, uric acid, and creatinine at 28 and 34 weeks as minimum for monitoring gestational hypertension or preeclampsia development 4
• Urinalysis at each visit to screen for proteinuria and preeclampsia 4

Modified Schedules for High-Risk Conditions

Obesity (BMI ≥35 kg/m²)

• Delayed anatomy scan at 20-22 weeks with repeat follow-up in 2-4 weeks if incomplete due to suboptimal visualization 3
• Growth scan at 28-32 weeks to aid detection of late-onset fetal growth restriction when clinical assessment is limited 3

Preeclampsia or Gestational Hypertension

• Immediate fetal biometry, amniotic fluid assessment, and Doppler studies at diagnosis 1
• Serial ultrasound evaluations every 2 weeks minimum for fetal growth, amniotic fluid, and umbilical artery Doppler from 24 weeks until birth 1
• Blood tests (hemoglobin, platelet count, liver transaminases, uric acid, creatinine) at 28 and 34 weeks minimum, with more frequent testing as clinically indicated 4

Multiple Gestations

• First trimester scan to determine chorionicity and amnionicity 3
• Anatomy scan at 18-22 weeks 3
• Serial growth scans every 3-4 weeks starting from the anatomy scan 3
• Weekly to biweekly monitoring starting at 16 weeks for monochorionic twins to screen for twin-twin transfusion syndrome 3

Important Clinical Caveats

Common Pitfalls to Avoid

• Failing to screen high-risk women early in pregnancy (those with BMI ≥30 kg/m² or prior gestational diabetes) results in delayed intervention and increased complications 1
• Not repeating gestational diabetes screening at 24-28 weeks in high-risk women who initially test negative leads to delayed diagnosis and treatment 1
• Performing unnecessary follow-up scans for isolated soft markers (like echogenic intracardiac focus or choroid plexus cysts) when aneuploidy screening is negative wastes resources 3
• Routine antenatal testing in low-risk pregnancies does not improve outcomes and may cause iatrogenic prematurity from false-positive results 1

Evidence-Based Flexibility

• Reduced visit schedules (8-10 visits instead of 12-14) produce equivalent maternal and neonatal outcomes for low-risk pregnancies, though this remains an evolving area of practice 1
• The traditional schedule dates from 1930 and lacks rigorous scientific evidence, but remains the current standard in most U.S. practices 4