Difference between mean gestational sac diameter and crown-rump length as a marker of first-trimester pregnancy loss after in vitro fertilization.

Objective: To investigate whether the difference between mean gestational sac diameter and crown-rump length (mGSD - CRL) is associated with first-trimester pregnancy loss or adverse pregnancy outcomes after in vitro fertilization (IVF) and to determine if mGSD - CRL is a better predictor of pregnancy loss than either measurement alone.

Design: Retrospective cohort study.

Setting: University hospital.