During the study period, there were a total of 5,481deliveries of
singleton gestations. Among these, 4,603 cases were delivered at
term, including 2,480 cases of nulliparas. Among these term
singleton nulliparas, 565 cases underwent induction of labor before
spontaneous onset of labor or ROM, without an intrauterine fetal
demise. The timing of ROM was not available in the medical
records of 10 cases. The remaining 555 cases were classified into
either an ‘‘early ROM’’ group or ‘‘late ROM’’ group according to
the timing of ROM, and additional 55 cases were excluded from
analysis (39 cases with pre-labor ROM and 16 cases in whom the
distinction between early ROM and late ROM was not possible
(13 cases in whom emergent cesarean section was performed
before a cervical dilatation of 4 cm with intact membranes, and 3
cases because artificial ROM was performed before a cervical
dilatation of 4 cm)). Finally, five hundred cases were eligible for
study and Table 1 lists the indications for labor induction in the
study population.