Comparison of active phase labor between triplet, twin, and singleton gestations

OBJECTIVE: To characterize the active phase of labor in triplet pregnancies and compare it with gestational age-matched twins and singletons. METHODS: Active phase rates were calculated beginning at 5 cm of dilation f or women with triplet gestations longer than 24 weeks who labored and reach ed the second stage. Twin and singleton cohorts that also completed the fir st stage of labor were matched for gestational age at delivery (+/-1 week), parity, and epidural use. Intrapartum variables included oxytocin use (ind uction or augmentation, duration of infusion, and maximum dosage), cervical dilation at membrane rupture, and active phase dilation rate. RESULTS: Thirty-two triplet pregnancies met inclusion criteria between Janu ary 1994 and September 1998 and were each compared with twin and singleton cases in a 1:2 ratio. Triplet and twin active phase rates, while similar (1 .8 versus 1.7 cm/hour, respectively), were significantly lower than the mea n singleton dilation rate (2.3 cm/hour, P =.02). No other intrapartum varia bles differed between the three groups. Despite controlling for gestational age at delivery, mean birth weights were significantly higher in singleton s and correspondingly lower in ttl,ins and triplets (2493 versus 2112 and 1 968 g, respectively; P =.001). An analysis of active phase dilation rates a s a function of the cumulative birth weight per pregnancy demonstrated an i nverse correlation, with slower progress in active labor associated with in creasing total fetal weight (R = -.24; P =.002). CONCLUSIONS: Triplet and twin active phase dilation proceeds at a slower ra te than that observed in singleton pregnancies. The 1 are of active phase d ilation is inversely correlated to total fetal weight. Copyright (C) 2000 b y the Society for Gynecologic Investigation.