Amnion rupture sequence in previable fetuses.

Amnion rupture sequence is considered an uncommon, sporadic condition among liveborn infants. We have examined 1,010 previable fetuses (9-20 weeks developmental age) to determine the incidence and nature of amnion rupture sequence at this stage of development. We found 18 affected fetuses (15 spontaneous and 3 induced abortions) with the incidence of 1:56. Eleven fetuses had limb constrictions and amputations only; 7 fetuses also had nonlimb involvement, including disruptions of the craniofacial region mimicking encephalocele, unusual facial clefts, and abdominal defects. In 6 pregnancies, constrictions of the umbilical cord by amniotic bands were the cause of fetal intrauterine death.