Initial Blood Work Recommended for Pregnancy

Essential First Trimester Laboratory Tests

• The American College of Obstetricians and Gynecologists recommends that all pregnant women undergo comprehensive blood work screening in the first trimester, including complete blood count, hepatitis B surface antigen, blood glucose screening, and blood typing to identify potential complications early and ensure optimal maternal and fetal outcomes 1, 2
• Screening for hepatitis B surface antigen (HBsAg) is recommended in the first trimester to recognize and reduce the risk of HBV mother-to-child transmission 3
• Rubella, syphilis, hepatitis B virus, and HIV testing should be performed during preconception counseling or at the first prenatal visit, as recommended by the American College of Obstetricians and Gynecologists 1
• Cervical cultures and Pap smear should be obtained at the initial visit, according to the American College of Obstetricians and Gynecologists 1

Hematologic Assessment

• Blood typing and antibody screening should be performed to identify potential blood incompatibilities, as recommended by the American Diabetes Association 1

Metabolic and Endocrine Screening

• Fasting blood glucose should be measured at the first prenatal visit to screen for pre-existing diabetes, according to the American Academy of Family Physicians 4, 5
• Risk assessment for gestational diabetes should be undertaken at the first prenatal visit, as recommended by the American Diabetes Association 6
• Women with high risk for gestational diabetes should undergo glucose testing as soon as feasible, according to the American Academy of Family Physicians 7
• Thyroid-stimulating hormone should be tested in women with pre-existing diabetes, as recommended by the American Diabetes Association 1

Renal Function Assessment

• Serum creatinine and urinary albumin-to-creatinine ratio should be measured, particularly in women with chronic hypertension or pre-existing diabetes, according to the American Diabetes Association 1
• Baseline renal function tests are important for women at risk of preeclampsia, as recommended by the American Heart Association 8, 9

Liver Function Assessment

• Liver enzymes and function tests should be performed in women with chronic hypertension, according to the American Heart Association 10
• Uric acid levels should be measured as elevated levels are associated with worse maternal and fetal outcomes, as recommended by the American Heart Association 10

Second Trimester Screening

Aneuploidy and Neural Tube Defect Screening

• Multiple marker screening should be offered to women unless amniocentesis is indicated based on history/age or they have elected first-trimester screening, according to the American College of Medical Genetics and Genomics 2
• Maternal serum alpha-fetoprotein (MSAFP) screening for detection of open neural tube defects and anencephaly should be offered between 16-18 weeks gestation, as recommended by the American College of Medical Genetics and Genomics 2

Diabetes Screening

• Women with average risk for gestational diabetes should have testing at 24-28 weeks of gestation, according to the American Academy of Family Physicians and the American Diabetes Association 6, 7
• A 50-g glucose challenge test or oral glucose tolerance test should be performed at 24-28 weeks, as recommended by the American Academy of Family Physicians 7

Special Considerations

Women with Chronic Hypertension

• More comprehensive baseline laboratory assessment is recommended, including complete blood count, liver enzymes, renal function, and uric acid, according to the American Heart Association 10
• These tests provide a baseline reference for detecting superimposed preeclampsia, which complicates up to 25% of pregnancies with chronic hypertension, as recommended by the American Heart Association 10

Women with Pre-existing Diabetes

• Additional testing should include A1C, thyroid-stimulating hormone, creatinine, and urinary albumin-to-creatinine ratio, according to the American Diabetes Association 1
• Comprehensive eye examination should be performed to assess for diabetic retinopathy, as recommended by the American Diabetes Association 1

Common Pitfalls to Avoid

• Failing to screen for hepatitis B in the first trimester, which is crucial for preventing mother-to-child transmission, according to the Journal of Hepatology 3
• Delaying glucose screening in high-risk women, which should be performed as early as possible in pregnancy, according to the American Academy of Family Physicians 7
• Overlooking the importance of baseline laboratory tests in women with chronic medical conditions, which are essential for monitoring disease progression and detecting complications, according to the American Heart Association and the American Diabetes Association 1, 10

Prenatal Laboratory Testing and Screening

First Trimester Screening

• Women with clinical characteristics suggesting high risk, such as marked obesity, prior gestational diabetes, or strong family history, should undergo glucose testing immediately, as recommended by the American Diabetes Association and the American Academy of Family Physicians 11, 12
• First trimester combined screening for aneuploidy includes nuchal translucency measurement, pregnancy-associated plasma protein A, and free beta-hCG or total hCG, achieving approximately 85-90% detection rate for Down syndrome with 5% false-positive rate, according to the American College of Medical Genetics and Genomics 13

Gestational Diabetes Screening

• All women not previously diagnosed with diabetes should undergo 50-gram glucose challenge test or oral glucose tolerance test at 24-28 weeks, as recommended by the American Diabetes Association 11
• Women with negative early testing but high-risk features should be retested at 24-28 weeks, according to the American Academy of Family Physicians 11, 12

Special Populations

• Post-bariatric surgery patients require expanded testing, including every trimester: CBC, serum ferritin, iron studies, transferrin saturation, serum folate, vitamin B12, and every 6 months: prothrombin time/INR, vitamin K1, serum protein/albumin, vitamin D with calcium/phosphate/magnesium/PTH, as recommended by the Obesity Society 14

First‑Trimester Prenatal Laboratory and Aneuploidy Screening Guidelines

Hematologic, Infectious, and Renal Screening (First Prenatal Visit)

• Complete blood count (CBC) should be performed at the initial visit to detect anemia and establish a baseline hemoglobin level in all pregnant women. 15
• Hepatitis B surface antigen (HBsAg) testing is recommended to identify carrier status and enable interventions that prevent vertical transmission of hepatitis B. 15
• HIV antibody testing should be offered universally to pregnant patients to allow early diagnosis and treatment. 15
• Syphilis serology (RPR or VDRL) is advised to detect maternal infection so that timely therapy can reduce fetal complications. 15
• Rubella IgG screening identifies non‑immune women who should receive postpartum vaccination to protect future pregnancies. 15
• Cervical cultures for Neisseria gonorrhoeae and Chlamydia trachomatis are indicated at the first visit to treat asymptomatic infections and reduce adverse pregnancy outcomes. 15
• Urinalysis is performed to screen for asymptomatic bacteriuria, proteinuria, and glucosuria, providing early clues to urinary‑tract infection or renal disease. 15

First‑Trimester Aneuploidy Screening (11–14 Weeks)

• Nuchal translucency (NT) ultrasound measurement between 11 weeks 4 days and 13 weeks 6 days is a core component of combined first‑trimester screening for chromosomal abnormalities. [16][17]
• Pregnancy‑associated plasma protein A (PAPP‑A) levels are typically reduced in fetuses with Down syndrome and are incorporated into the risk algorithm. [18][17]
• Free β‑human chorionic gonadotropin (β‑hCG) concentrations are usually elevated in Down‑syndrome pregnancies and contribute to the combined risk calculation. [18][17]
• The combined first‑trimester screen (NT + PAPP‑A + β‑hCG) achieves an overall detection rate of ≈ 85–92 % for Down syndrome with a false‑positive rate of 1–5 %. 16

Quality Assurance for Nuchal Translucency Measurement

• Sonographer training and certification through dedicated quality‑assurance programs are required for accurate NT measurement; untrained operators produce unreliable results. 16
• NT measurements performed outside the 11 weeks 4 days to 13 weeks 6 days window are not valid for aneuploidy risk assessment and should be repeated within the appropriate gestational age range. 16

Second‑Trimester Neural‑Tube‑Defect Screening

• Maternal serum alpha‑fetoprotein (MSAFP) testing between 16–18 weeks is recommended for women who have undergone first‑trimester screening or chorionic‑villus sampling to evaluate the risk of neural‑tube defects. [16][17]