[Shorter delivery time after induction with misoprostol]

Increasing evidence has demonstrated that intravaginal misoprostol (PGE1) is more effective in labor induction than dinoprostone (PGE2). Several studies have demonstrated that the administration of PGE1 instead of PGE2 reduces the induction-to-delivery interval. However, it has not been fully investigated on which phase of birth the activity of PGE1 is stronger than that of PGE2. We undertook this study to investigate whether the activity of the two prostaglandins are different over time during the induction-to-delivery interval.

155 patients undergoing induction of labor with 50 micrograms intravaginal PGE1 were compared with 174 patients treated with 3 mg PGE2. In both groups the procedure was repeated 6, and 24 hours after the first dose until labor was achieved. Induction-to-initiation of labor time, duration of labor stages, induction-to-delivery time, mode of delivery, maternal and neonatal morbidity and changes in Bishop score were compared.

Demographic characteristics, indications for induction, mode of delivery, fetal weight, maternal and neonatal morbidity and duration of the labor stages were similar between the groups. A significant difference was found in terms of: induction-to-initiation of labor interval (7.37 h [1-68] vs. 11.25 h [1-74], p < 0.01) and induction-to-delivery interval (11.5 h [2.5-89] vs. 14.4 h [2.7-94], p < 0.05). The Bishop score at the time of the second administration was significantly different from that at admission in the PGE1 group compared to the PGE2 group [PGE1: 4.8 +/- 2/5.6 +/- 1.9, p < 0.0005; PGE2: 3.9 +/- 2/4.2 +/- 1.4, p = 0.09]. This effect of PGE1 remained significant after correction for various explanatory variables.

The stronger effect of PGE1 is the consequence of a faster cervical ripening, which in turn leads to a quicker achievement of active labor.

Intravaginal PGE1 compared to PGE2 reduces significantly the induction-to-delivery time.