Normal labor curve is affected by fetus gender: A cohort study.

Fetal male gender may affect the progression of labor and could be a risk factor for labor arrest. This study was conducted to evaluate the effect of fetus gender on labor curve. In this cohort study, 1550 singleton term pregnant women in labor phase (either spontaneous or by induction) were enrolled. Results of regular cervical examination, dilation, length of labor stages, mode of delivery, and sex of the fetus, and birth weight were recorded for all participants. Labor progression curve was compared between two sex groups with independent t test and chi2 test. : Finally, 1527 women completed the study (47.8% female and 52.1% male). Mean duration from beginning of the active phase up to full dilatation, from 4 to 6 cm, 6 to 8 cm, and 8 to 10 cm dilatations, were significantly longer in the male sex group compared to the female (p˂0.05). All durations were also significantly different when parity was considered (p˂0.05). We could not show fetal sex as an independent risk factor for active phase arrest (OR Adjusted: 1.18, CI 95% 1.01:1.42). Active phase stage was slower and longer in women who carried male fetuses compared to those carrying female fetuses; however, fetal sex did not increase the risk of active phase arrest.