Identifying fetal abnormalities

Key points Days 18–55 postconception is the time of maximal teratogenic potential when most organs are differentiating Teratogenic effects of medications may affect both organ structure and organ function Detailed ultrasound assessment of the fetus by trained personnel should detect most major structural abnormalities, but minor abnormalities are often undetected Patients at risk of neural tube defects (NTDs) should have 5 mg of folic acid daily for a minimum of 6 wk prior to conception