Twin and singleton latent phase duration in labor induction: A multicenter matched cohort study.

OBJECTIVE: To compare the duration of the latent phase in labor induction between twin and singleton pregnancies. METHODS: We performed a retrospective matched cohort study in two tertiary unit centers. Twin pregnancies accounted for the cases, and singleton pregnancies constituted the controls. Inclusion criteria were pregnancies induced by oxytocin or artificial rupture of the membranes. Each control was matched to each twin pregnancy according to maternal age, birthing center, parity, gestational age, body mass index and Bishop score. We compared the median durations of each labor phase, censoring pregnancies at delivery in cases of cesarean section. We conducted multivariable survival analysis, taking into account the variables that influenced the duration of the latent phase. RESULTS: We included 294 twin pregnancies matched to 294 singleton pregnancies. The median [IQR] duration of the latent phase of labor was significantly longer in twin pregnancies (6.3[4.4-8.6] hours) compared to singletons (4.2[3.2-5.8] hours, p < 0.01). This difference was also significant for the active phase (1.9[1.2-3.5] hours; 1.5[0.9-2.3] hours, p < 0.01), the first stage (7.7[5.3-10.8] hours; 5.3[3.9-7.5] hours, p < 0.01), the second stage (1.6[0.6-2.5] hours; 1.0 [0.3-2.3] hours, p < 0.01), and the median total induction duration (9.5[6.8-13.4] hours; 6.7[4.8-9.3] hours, p < 0.01). Twin pregnancies were significantly associated with latent phase duration (HR0.58, 95 %CI[0.48;0.71], p < 0.01) in the multivariable survival analysis. CONCLUSION: Twin pregnancies have a significantly longer latent phase in labor induction than singleton pregnancies.