Induction of labor and nulliparity: A nationwide clinical practice pilot evaluation

Induction of labor has become an increasingly common obstetric procedure, but in nulliparous women or women with a previous cesarean section, it can pose a clinical challenge. Despite an overall expansion of medical indications for labor induction, there is little international consensus regarding the criteria for induction, or for the recommended methods among nulliparous women. In this light, we assessed variations in the practice of induction of labor among 21 birth units in a nationwide cohort of women with no prior vaginal birth.

We carried out a prospective observational pilot study of women with induced labor and no prior vaginal birth, across 21 Norwegian birth units. We registered induction indications, methods and outcomes from 1 September to 31 December 2018 using a web-based case record form. Women were grouped into "Nulliparous term cephalic", "Previous cesarean section" and "Other Robson" (Robson groups 6, 7, 8 or 10).

More than 98% of eligible women (n=1818) were included and a wide variety of methods was used for induction of labor. In nulliparous term cephalic pregnancies, cesarean section rates ranged from 11.1% to 40.6% between birth units, whereas in the previous cesarean section group, rates ranged from 22.7% to 67.5%. The indications "large fetus" and "other fetal" indications were associated with the highest cesarean rates. Failed inductions and failure to progress in labor contributed most to the cesarean rates. Uterine rupture occurred in two women (0.11%), both in the previous cesarean section group. In neonates, 1.6% had Apgar <7 at 5 minutes, and 0.4% had an umbilical artery pH <7.00.

Cesarean rates and applied methods for induction of labor varied widely in this nationwide cohort of women without a prior vaginal birth. Neonatal outcomes were similar to those of normal birth populations. Results could indicate the need to move towards more standardized induction protocols associated with optimal outcomes for mother and baby.