Reproductive System

400-800 mcg/day, started ideally at least 1 month before conception and continued through the first trimester; 4 mg/day for women with a prior NTD-affected pregnancy.

By crown-rump length on ultrasound, which is the most accurate dating method; last menstrual period (Naegele rule) is used when reliable.

Add 7 days to the first day of the last menstrual period, subtract 3 months, and add 1 year (assumes a regular 28-day cycle).

CBC, blood type and Rh with antibody screen, rubella immunity, hepatitis B surface antigen, HIV, syphilis (RPR/VDRL), urinalysis/culture, and cervical cancer screening if due; offer chlamydia/gonorrhea screening.

At 24-28 weeks, typically with a 50 g 1-hour glucose challenge; if abnormal, confirm with a 100 g 3-hour oral glucose tolerance test.

Rectovaginal culture at 36 0/7 to 37 6/7 weeks; a positive screen (or GBS bacteriuria or prior GBS infant) warrants intrapartum IV penicillin prophylaxis.