What labs should be ordered for a prenatal panel in a female of childbearing age with potential risk factors such as previous pregnancies, miscarriages, or pre-existing medical conditions like gestational diabetes or hypertension?

Prenatal Laboratory Panel

All pregnant women should undergo comprehensive first-trimester laboratory screening including complete blood count, blood typing with antibody screen, hepatitis B surface antigen, syphilis, HIV, rubella immunity, urinalysis, and glucose screening, with additional testing at 24-28 weeks for gestational diabetes. 1

First Trimester Laboratory Tests (Initial Prenatal Visit)

Infectious Disease Screening

• Hepatitis B surface antigen (HBsAg) testing is mandatory in the first trimester to identify carriers and prevent mother-to-child transmission 1
• HIV, syphilis, and rubella testing should be performed at the first prenatal visit 1
• Cervical cultures and Pap smear should be obtained at the initial visit 1

Hematologic Assessment

• Complete blood count (CBC) to screen for anemia 1
• Blood typing (ABO and Rh) with antibody screening to identify potential blood incompatibilities and prevent hemolytic disease of the newborn 1, 2

Metabolic and Diabetes Screening

• Fasting blood glucose should be measured at the first prenatal visit in women with risk factors for diabetes (obesity, prior gestational diabetes, strong family history, advanced maternal age, non-White race/ethnicity) using standard diagnostic criteria 3, 1
• Women with risk factors should be tested immediately rather than waiting until 24-28 weeks 3, 1

Urinalysis

• Baseline urinalysis is recommended at the first visit, though evidence for routine repeated urinalysis throughout pregnancy is variable 2

Additional First Trimester Tests for High-Risk Women

Women with Chronic Hypertension

• Complete blood count, liver enzymes (AST, ALT), serum creatinine, and uric acid provide baseline values essential for detecting superimposed preeclampsia, which complicates up to 25% of pregnancies with chronic hypertension 1
• Urinary albumin-to-creatinine ratio should be measured 1

Women with Pre-existing Diabetes

• Hemoglobin A1C to assess glycemic control 1
• Thyroid-stimulating hormone (TSH) 1
• Serum creatinine and urinary albumin-to-creatinine ratio 1
• Comprehensive eye examination to assess for diabetic retinopathy 1

Second Trimester Screening (16-28 Weeks)

Neural Tube Defect Screening

• Maternal serum alpha-fetoprotein (MSAFP) should be offered between 16-18 weeks gestation for detection of open neural tube defects and anencephaly 1
• Multiple marker screening should be offered unless amniocentesis is indicated or first-trimester screening was elected 1

Gestational Diabetes Screening (24-28 Weeks)

• All pregnant women not previously diagnosed with diabetes should undergo screening at 24-28 weeks gestation 3, 1
• Either a 50-gram glucose challenge test (two-step approach) or 75-gram oral glucose tolerance test (one-step approach) may be used depending on regional preferences 3
• Women with negative early testing but high-risk features should be retested at 24-28 weeks 1

Preeclampsia Screening

• Blood pressure measurements should be obtained at each prenatal visit throughout pregnancy using proper technique (sitting position, legs uncrossed, back supported, arm at heart level, appropriate cuff size for arm circumference ≥33 cm) 3

Special Population Considerations

Post-Bariatric Surgery Patients

These patients require expanded testing every trimester including 1:

• CBC, serum ferritin, iron studies, transferrin saturation
• Serum folate and vitamin B12

Every 6 months 1:

• Prothrombin time/INR, vitamin K1
• Serum protein/albumin
• Vitamin D with calcium, phosphate, magnesium, and parathyroid hormone (PTH)

Critical Pitfalls to Avoid

• Never delay glucose screening in high-risk women—testing should occur at the first prenatal visit, not at 24-28 weeks 3, 1
• Never skip hepatitis B screening in the first trimester, as this is crucial for preventing vertical transmission 1
• Never overlook baseline laboratory assessment in women with chronic hypertension or diabetes, as these provide essential reference values for detecting complications like superimposed preeclampsia 1
• Never use improper blood pressure measurement technique, as this can lead to false readings and missed preeclampsia diagnoses 3