SummaryMaternal serum alpha-fetoprotein increases slowly over 20 hours after the intra-amniotic injection of prostaglandin E2for mid-trimester termination of pregnancy. When hypertonic urea is injected together with the prostaglandin, the rise in maternal alpha-fetoprotein is much greater and occurs much more rapidly. The increase in maternal alpha-fetoprotein is not accompanied by transplacental passage of fetal red cells. It is suggested that alpha-fetoprotein passes through to the maternal circulation as a direct result of severe fetal compromise leading to fetal death