What serology tests are recommended for a pregnant woman of childbearing age with no prior prenatal care?

Serology Testing for Mothers Without Prenatal Care

For pregnant women presenting without prenatal care, immediately perform a comprehensive serology panel including HIV, syphilis, hepatitis B surface antigen (HBsAg), and consider testing for gonorrhea, chlamydia, rubella immunity, and blood type/Rh status. 1, 2

Essential First-Line Serology Tests

HIV Testing (Highest Priority)

• Perform expedited HIV testing immediately using either rapid testing with confirmation or standard testing with expedited results, as women without prenatal care have significantly higher HIV prevalence (15% receive no prenatal care vs. 2% in general population) 1
• HIV transmission rates are dramatically higher without prenatal care: 17.5% with no prenatal care vs. 8.0% with >3 prenatal visits 1
• Testing should be performed as soon as the mother's medical condition permits, even during labor and delivery if necessary 1
• Use opt-out approach where testing is recommended but voluntary 1, 2

Syphilis Serology

• Perform both treponemal and non-treponemal testing immediately 1, 2
• This is mandatory in all states and critical because no infant should be discharged without maternal syphilis status determined 1
• If the woman delivers a stillborn infant, syphilis testing is essential 1
• Repeat testing at delivery is recommended for high-risk women 1, 2

Hepatitis B Surface Antigen (HBsAg)

• Test for HBsAg immediately as this is universally recommended at first prenatal contact 1, 2
• This is critical because infants born to HBsAg-positive mothers require hepatitis B vaccine and hepatitis B immune globulin (HBIG) within 12 hours of birth 2
• HBsAg-positive women must be reported to local/state health departments for case management 1

Gonorrhea and Chlamydia Testing

• Perform testing for both pathogens, particularly in women at risk or in high-prevalence areas 1
• Testing is recommended for all pregnant women under 25 years or those at increased risk 2

Additional Important Serology Tests

Rubella Immunity

• Test for rubella IgG antibody status 2, 3
• If susceptible (negative), postpartum vaccination should be documented, though adherence is often suboptimal (only 65.7% receive recommended vaccination) 4

Blood Type and Antibody Screen

• Perform ABO/Rh typing and antibody screen 2

Hepatitis C (Risk-Based)

• Test for hepatitis C antibody if history of injection drug use or blood transfusion/organ transplant before 1992 2

Critical Timing Considerations

If the woman presents during labor and delivery:

• Perform rapid HIV testing to allow for intrapartum and neonatal antiretroviral prophylaxis, as efficacy is greatest within 12 hours of birth 1
• The goal is identifying HIV-infected women as soon as possible because prophylactic therapy efficacy decreases with time 1

If presenting in third trimester:

• All the above tests should be performed immediately 1, 2
• Consider repeat testing at delivery for syphilis and HBsAg in high-risk women 1, 2

Common Pitfalls to Avoid

• Never delay HIV testing in women without prenatal care, as this population has the highest HIV prevalence and transmission rates 1
• Do not rely on single syphilis test—both treponemal and non-treponemal results are required for proper diagnosis 2
• Avoid risk-based HIV screening alone—universal opt-out screening identifies more infected women 2
• Do not skip hepatitis B testing even if the woman reports prior vaccination, as breakthrough infections occur 2
• Inadequate prenatal care is the strongest predictor of missed screening opportunities (relative risk 14.6), making immediate comprehensive testing essential 4

Additional Considerations for Specific Populations

• Women with injection drug use history require hepatitis C testing and are at highest risk for lacking prenatal care (35% vs. 6% for non-drug users) 1
• Black women are less likely to receive adequate prenatal care and testing, yet more likely to test positive for HBsAg and syphilis, making immediate comprehensive screening particularly important 4