The role of the fetus in the onset and progress of stretch-induced labor and in the change in amniotic fluid prostaglandin F2 alpha and plasma prostaglandin F2 alpha metabolite levels was evaluated in six normal pregnant women (group 1) and six women whose fetuses had been dead for more than one week (group 2). The uterus was distended by a balloon inflated with physiologic saline. Regular uterine contractions occurred, and increased in all patients. Within 21 hours, all patients delivered a normal baby in group 1 and a macerated fetus in group 2. There was no significant difference in induction-delivery interval between the two groups. Both groups showed a significant and similar range of increases in the levels of amniotic fluid prostaglandin F2 alpha and plasma prostaglandin F2 alpha metabolite during treatment (P less than 0.001). Thus, the fetus has no functional role in the onset and progress of stretch-induced labor or in the rise of amniotic fluid prostaglandin F2 alpha and plasma prostaglandin F2 alpha metabolite levels.