Ultrasonic evaluation of twin pregnancies associated with raised serum alpha-fetoprotein levels.

Five cases of twin pregnancy associated with elevated maternal serum alpha-fetoprotein levels are presented. In each instance an abnormality was detected by ultrasound examination--in four cases this represented anomalous development of one or both fetuses: discordant anencephaly; a monozygotic heterokaryotypic twin pregnancy with coexistent Turner's syndrome and intrauterine death; concordant body-stalk syndrome; and fetal exomphalos together with an acardiac monster. In the remaining case, there had been an intrauterine death of one of the twins. Ultrasound examination proved valuable in all instances; three pregnancies were terminated and single healthy infants were delivered from each of the other two pregnancies.