Differences in starting points of active phase and labor duration between preterm and full-term primiparae

Abstract

Objective To compare the starting points of the active phase of labor and labor duration between preterm and full-term primiparae and to provide evidence for appropriate labor management. Methods From January 2013 to December 2016, 925 preterm primiparae (preterm group, 28 to 36+6 weeks) and equal number of full-term primiparae (full-term group, 37 to 41+6 weeks) who delivered in Tianjin Central Hospital of Gynecology Obstetrics were recruited. The starting point of the active labor was defined as the cervical dilatation at the turning point on the cervical dilatation curve where changing from almost flat to the biggest slope. Differences in the starting points and labor duration between the two groups were compared. Statistical analysis was performed using two independent sample t-test, one way analysis of variance and rank-sum test. Results The duration of the first and second stages [(5.7±2.5) vs (6.8±5.2) h, t=-5.835; (29.9±16.8) vs (34.2±17.2) min, t=-12.637; both P 6 cm of cervical dilatation were 74 (8.0%), 208 (22.5%), 287 (31.0%), 168 (18.2%), 127 (13.7%) and 61(6.6%), respectively. In the preterm group, the starting points of the active phase at cervical dilatation≤3 cm, ≤4 cm and ≤5 cm accounted for 60.3% (558/925), 82.3% (761/925) and 94.1% (870/925), respectively. In the full-term group, the percentages of the active phase starting at cervical dilatation≤4 cm, ≤5 cm and ≤6 cm were 61.5% (569/925), 79.7% (737/925) and 93.4% (864/925), respectively. Conclusions Preterm primiparae may experience shorter labor duration and an earlier start of the active phase than full-term primiparae. The routine labor progression model for full-term primiparae should not be applied to preterm primiparae. Key words: Obstetric labor, premature; Term birth; Labor, obstetric; Fetal monitoring; Labor stage, first; Labor stage, second