Turn an estimated due date into US timing windows and result dates for common prenatal screening and diagnostic tests.

Compare estimated miscarriage risk now with the risk at a future gestational week to help choose an announcement date.

Compare two quantitative hCG results to see whether the pattern better fits falling residual hCG or new hCG production.

Find how many days of backup protection may be needed when starting or switching birth control under current US CDC rules.

Compare two intercourse dates with an ultrasound-based conception window to see whether timing favors one possible father.

Estimate gestational-sac or yolk-sac visibility on transvaginal ultrasound and a possible scan date from an hCG trend.

Estimate vanishing-twin interference concern for an NIPT blood draw using timing, gestational age, and ultrasound type.

Estimate the chance that an NIPT redraw will return a result after a low-fetal-fraction no-call and find the first study-based redraw date.

Estimate procedure-related loss risk and the chance standard testing finds a missed trisomy after low-risk NIPT.

Estimate live-birth outcomes without trisomy 21, trisomy 18, or trisomy 13 before NIPT or after a screening result.