Infectious Diseases in Pregnancy
Core concepts
Understand the TORCH infections and their prenatal implications, but recognize that the mnemonic is a starting point, not a complete list. Know group B streptococcus screening and prophylaxis, HIV management to prevent vertical transmission, syphilis screening and treatment, hepatitis B and C implications, and varicella and rubella immunity. Understand cytomegalovirus as a leading cause of congenital hearing loss and the limits of prenatal diagnosis. Know toxoplasmosis and listeriosis prevention and the role of Zika and other emerging infections.
Understand influenza and COVID-19 risks in pregnancy and the importance of vaccination. Know the principles of antimicrobial selection in pregnancy and the contraindications to certain agents (e.g., tetracyclines, fluoroquinolones in some contexts). Understand sepsis in pregnancy and the importance of early recognition.
Traps
- Assuming all IgM positivity indicates acute infection; confirm with IgG avidity or repeat testing.
- Forgetting that GBS prophylaxis is intrapartum, not antepartum treatment.
- Missing that syphilis can be treated with penicillin and that desensitization may be needed.
- Overlooking that HIV viral load and adherence determine transmission risk.
- Assuming all vaccines are contraindicated in pregnancy; inactivated vaccines are generally safe.
Rule of thumb
For any infection in pregnancy, ask: what is the maternal risk, what is the fetal risk, and what is the safest effective treatment? Then consider prevention for future pregnancies.
Worked example: A pregnant patient has a positive syphilis screen. Confirm with a treponemal test, stage the infection, and treat with penicillin. If she is allergic, desensitization is preferred over alternative regimens because penicillin is the only proven regimen for preventing congenital syphilis.