Reassessing the duration of each stage of labor and their relation to postpartum hemorrhage in the current Japanese population.

Abstract

To reassess the normal duration of each stage of labor in a contemporary Japanese cohort, and to determine whether prolongation of each stage of labor increases the rate of postpartum hemorrhage (PPH) in vaginal deliveries. Clinical data of women who delivered at term at 12 facilities between 2012 and 2018 were retrospectively collected. A total of 31 758 women were subdivided into three or four subgroups according to the duration of each stage of labor and parity. Univariate and multivariate logistic regression analyses were performed to estimate crude and adjusted odds ratios (ORs) of PPH (blood loss ≥ 1000 mL) in each subgroup, with women with the shortest durations in each subgroup used as the reference group. The reference range of each stage of labor was found to be shorter than that previously reported. Women with prolonged second (primiparity, adjusted OR: 1.15-1.78; multiparity, adjusted OR: 1.14-1.74) and third (primiparity, adjusted OR: 1.39-4.95; multiparity, adjusted OR: 1.46-3.80) stages of labor showed an increased risk of PPH, whereas those with prolonged first stage did not. A significantly increased risk of PPH was found both in primiparous and multiparous women with third stages of labor ≥ 5min. The normal duration of each stage of labor in the Japanese population needs to be revised and well-recognized by obstetric care providers. A prolonged third stage of labor was a more important contributing factor to PPH than prolonged first or second stages.