Genetics, Teratology, and Medication Safety in Pregnancy
Core concepts
Understand inheritance patterns (autosomal dominant, autosomal recessive, X-linked) and common aneuploidies (trisomy 21, 18, 13; sex chromosome differences). Know the critical periods of teratogenesis (organogenesis in the first trimester) and classic teratogens: isotretinoin, warfarin, valproate, carbamazepine, methotrexate, ACE inhibitors/ARBs, and tetracyclines. Understand that many medications lack strong evidence of harm and that untreated disease can be riskier than treatment. Preconception counseling includes folic acid supplementation to reduce neural tube defects and carrier screening based on ethnicity and family history.
Traps
Questions often test that a drug "category" label is not a substitute for individualized risk assessment. Another trap is assuming all antiseizure medications carry equal teratogenic risk - valproate is highest. Also, folic acid reduces but does not eliminate neural tube defect risk.
Rule of thumb
When evaluating a medication in pregnancy, consider timing of exposure, dose, indication, and alternatives; for teratogens with no alternative, counsel and optimize rather than automatically discontinue.