Recommended Prenatal Laboratory Tests for Pregnant Individuals
All pregnant individuals should undergo comprehensive prenatal laboratory screening to identify potential health risks and prevent complications affecting maternal and fetal outcomes.
First Prenatal Visit (Ideally Before 12 Weeks)
Blood Tests
- Complete blood count (CBC) to assess for anemia and platelet abnormalities 1
- Blood type and Rh status with antibody screen (high strength of evidence) 2
- Rh-negative women require Rh immune globulin at 28 weeks gestation 2
- Infectious disease screening:
- Genetic carrier screening based on family history, ethnicity, and risk factors 2
Urine Tests
- Urinalysis and urine culture for asymptomatic bacteriuria 5
- Chlamydia and gonorrhea screening (especially for high-risk populations) 3, 4
Supplementation
- Folic acid supplementation (400-800 mcg daily) to prevent neural tube defects 6, 5
- Higher doses may be needed for women with specific risk factors
Second Trimester (15-20 Weeks)
Genetic Screening
- Maternal serum AFP screening for neural tube defects, optimally between 16-18 weeks 3
- Multiple marker screening (quad screen) including:
Anatomic Assessment
- Detailed ultrasound for fetal anatomy assessment at 18-22 weeks 2
24-28 Weeks
Metabolic Screening
- Gestational diabetes screening using 50g oral glucose challenge test 2, 5
- Follow-up with 3-hour glucose tolerance test if initial screen is abnormal
Hematologic Assessment
- Repeat CBC to assess for pregnancy-related anemia
- Administration of Rh immune globulin for Rh-negative women 2
35-37 Weeks
Infectious Disease Screening
- Group B Streptococcus (GBS) vaginal-rectal culture 3, 4
- Positive results require intrapartum antibiotic prophylaxis to prevent neonatal infection
Special Considerations
High-Risk Pregnancies
- Hepatitis C antibody testing for women with history of injection drug use or transfusion/organ transplant before 1992 3
- Tuberculosis screening for women who use drugs illicitly 3
- Aspirin 81mg daily starting at 12 weeks for women at risk of preeclampsia 5
Imaging Considerations
- Ultrasound without contrast is the preferred imaging modality throughout pregnancy 3
- MRI without gadolinium is preferred over CT when advanced imaging is needed 3
- Abdominal CT without contrast is generally safe but cumulative radiation exposure should be kept below 50 mGy 3
Implementation Considerations
Documentation Requirements
- The Joint Commission requires documentation of maternal disease status for HIV, hepatitis B, syphilis, and GBS in both maternal and newborn medical records 4
- Immediate peripartum testing is required for women with inadequate prenatal screening 4
Testing Refusal
- While universal testing is recommended, testing should remain voluntary 3
- Women who refuse testing should not be coerced, denied care, or threatened with negative consequences 3
- Providers should address reasons for refusal through education and trust-building 3
Pitfalls to Avoid
- Delayed initiation of prenatal care - care initiated at 10 weeks or earlier improves outcomes 5
- Risk-based testing approaches identify fewer HIV-infected women than universal screening 3
- Failure to retest women who initially refuse testing or who are at ongoing risk 3
- Inadequate follow-up of positive screening results 4
- Incorrect gestational age dating affecting interpretation of screening results 2
Proper implementation of these prenatal laboratory tests significantly reduces maternal and fetal morbidity and mortality by enabling early detection and management of conditions that could adversely affect pregnancy outcomes.