Antepartum Care
Antepartum questions reward a systematic approach: establish gestational age and risk status first, then interpret every lab and surveillance result against that gestational age.
Dating and risk stratification
Naegele's rule uses the first day of the last menstrual period: subtract 3 months, add 7 days, then adjust for cycle length. An ultrasound before 14 weeks is the most accurate dating method and supersedes LMP when the two disagree by more than about a week. GTPAL records gravidity and outcomes: term births, preterm births, abortions (including losses before 20 weeks), and living children. A frequent trap is counting a 22-week loss as an abortion (it is a preterm birth) or counting the current pregnancy as a living child.
Screening and laboratory work
Routine studies include blood type, Rh, and antibody screen; CBC; rubella and varicella immunity; HBsAg; HIV; syphilis; urine culture; aneuploidy screening; a 1-hour glucose challenge at 24–28 weeks; and group B streptococcus culture at 36 0/7–37 6/7 weeks. Rh-negative, unsensitized patients receive RhoGAM at about 28 weeks and within 72 hours of delivering an Rh-positive infant. If the antibody screen already shows anti-D, the patient is sensitized and RhoGAM is not the answer.
Hypertensive disorders and diabetes
Preeclampsia is new hypertension after 20 weeks plus proteinuria or end-organ features; proteinuria is not required when severe features are present. Chronic hypertension predates 20 weeks or persists beyond 12 weeks postpartum. Gestational diabetes is classified A1 (diet-controlled) or A2 (medication).
Worked example
If the LMP was March 10, subtract 3 months (December 10) and add 7 days, giving December 17 as the EDD. That date, not fundal height, anchors every later decision about surveillance and delivery timing.