First Prenatal Visit Laboratory Testing
All pregnant women should undergo a comprehensive laboratory panel at the first prenatal visit, including complete blood count, blood type with antibody screen, hepatitis B surface antigen, HIV, syphilis, rubella immunity, urinalysis, and fasting blood glucose. 1, 2
Essential First Trimester Laboratory Tests
Hematologic Assessment
- Complete blood count (CBC) to screen for anemia and establish baseline values 1, 2
- Blood type and Rh status with antibody screen to identify blood incompatibilities and determine need for Rho(D) immune globulin 1, 2, 3
Infectious Disease Screening
- Hepatitis B surface antigen (HBsAg) to prevent mother-to-child transmission 1, 2, 4
- HIV antibody testing to enable early treatment and prevent vertical transmission 1, 2, 4
- Syphilis serology (RPR or VDRL) to detect and treat infection early 1, 2, 4
- Rubella antibody status to identify susceptible women requiring postpartum vaccination 1, 2, 3
Metabolic Screening
- Fasting blood glucose at the first prenatal visit to screen for pre-existing diabetes 1, 2
- Women with clinical characteristics suggesting high risk (marked obesity, prior gestational diabetes, strong family history) should undergo glucose testing immediately 5
Additional First Visit Testing
- Urinalysis and urine culture to screen for asymptomatic bacteriuria 3
- Cervical cytology (Pap smear) if due per routine screening guidelines 1
- Hepatitis C antibody especially in women with risk factors 2
Risk-Based Additional Testing
Women with Pre-existing Diabetes
- Hemoglobin A1C for glycemic control assessment 1, 2
- Thyroid-stimulating hormone (TSH) 5, 1, 2
- Serum creatinine and urinary albumin-to-creatinine ratio for renal function 1, 2
- Comprehensive eye examination for diabetic retinopathy 1
Women with Chronic Hypertension
- Baseline liver enzymes (AST, ALT) 1, 2
- Serum creatinine for renal function 1, 2
- Uric acid as elevated levels predict worse outcomes 1, 2
- These baseline values are critical for detecting superimposed preeclampsia, which complicates up to 25% of pregnancies with chronic hypertension 1
Women with Thyroid Disease Risk Factors
- TSH testing should be considered in women with personal or family history of thyroid disease, symptoms, or type 1 diabetes 1, 2
Aneuploidy Screening (11-14 Weeks)
First trimester combined screening includes:
- Nuchal translucency (NT) measurement via ultrasound 5, 2
- Pregnancy-associated plasma protein A (PAPP-A) 5, 2
- Free beta-hCG or total hCG (free beta-hCG performs better at 11-12 weeks; total hCG may perform slightly better at 13 weeks) 5
- This combination achieves approximately 85-90% detection rate for Down syndrome with 5% false-positive rate 5, 2
Second Trimester Follow-Up Testing
Gestational Diabetes Screening (24-28 Weeks)
- 50-gram glucose challenge test or oral glucose tolerance test for all women not previously diagnosed with diabetes 5, 1, 2
- Women with negative early testing but high-risk features should be retested at 24-28 weeks 5
Neural Tube Defect Screening (16-18 Weeks)
- Maternal serum alpha-fetoprotein (MSAFP) should be offered even to women who had first trimester aneuploidy screening 1, 2
Late Third Trimester (36-37 Weeks)
Critical Pitfalls to Avoid
- Never delay hepatitis B screening beyond the first trimester, as this is essential for preventing vertical transmission and implementing appropriate delivery protocols 1, 2
- Do not postpone glucose testing in high-risk women (obesity, prior gestational diabetes, family history)—test immediately at first visit rather than waiting until 24-28 weeks 5, 1
- Failing to obtain baseline laboratory values in women with chronic conditions (hypertension, diabetes) eliminates the ability to detect superimposed complications like preeclampsia 1, 2
- Not documenting maternal infectious disease status violates Joint Commission requirements and compromises neonatal care planning 4