PROGRESSION OF LABOR IN TWIN VERSUS SINGLETON GESTATIONS

OBJECTIVE: The aim of this study was to investigate whether labor curv es of twin gestations differ from those of singleton gestations. STUDY DESIGN: Among 1821 twin deliveries at our institution (1984-1996), we found 69 nulliparous and 94 multiparous women who were delivered at t erm (greater than or equal to 37 weeks) of a vertex twin A with a birt h weight of greater than or equal to 2500 g. We excluded women who had any of the following: induction of labor, oxytocin augmentation, cerv ical dilatation >6 cm on admission, tocolysis during the previous 14 d ays, height <150 cm, hypertension, and diabetes. Women with singleton gestations (n = 163) who met the same exclusion criteria were matched for parity and maternal age (+/-3 years). Stage 1 of labor was defined as the interval between 4 and 10 cm cervical dilatation. Kaplan-Meier survival analysis was used for comparison between the groups. RESULTS : The study and control groups were similar in mean maternal height; h owever, women with twins were significantly heavier than were those wi th singletons (79.3 +/- 11.2 kg vs 73.2 +/- 10.8 kg, P < .001), had a higher frequency of epidural anesthesia (82% vs 62%), and had a signif icantly lower birth weight of the presenting fetus (2779.1 +/- 242.5 g vs 3301.4 +/- 429.2 g, P < .001). The cervical effacements and vertex stations on admission were similar in the 2 groups. On admission the cervical dilatation of women delivered of twins was smaller than that of the control group. Twin gestations had a significantly shorter firs t stage of labor than did their matched singleton control gestations ( 3.0 +/- 1.5 hours vs 4.0 +/- 2.6 hours, P < .0001). This difference wa s apparent only in nulliparous women. No statistical difference was no ted in the mean length of the second stage of labor (0.8 +/- 0.5 hour for twins and 0.7 +/- 0.6 hour for singletons). CONCLUSION: Twin gesta tions have a significantly shorter first stage of labor than do single ton gestations. This difference may be the result of the birth weight of the presenting twin being lower than that of its singleton counterp art or to differences in uterine contractility in twin and singleton g estations. Different labor curves should be considered for managing tw in deliveries.