Duration of the second stage of labour and risk of subsequent spontaneous preterm birth

Abstract

Objectives: To determine the risk of spontaneous preterm birth (sPTB) associated with the length of second stage of labour in the first term delivery. Design: Retrospective cohort study. Setting: University hospital. Population: Women with first two consecutive singleton births and the first birth at term. Those who did not reach the second stage of labour in the first delivery were excluded. Methods: Charts from 2007 to 2019 were reviewed. Main outcome measures: Rate of sPTB (<37 weeks of gestation) in the second delivery.Results: Of 13 958 women who met study inclusion criteria, 1464 (10.5%) parturients had a prolonged second stage (≥180 min) in their first term delivery. The rate of sPTB in the second delivery was similar in those with and without a prolonged second stage in first delivery (2.8% versus 2.8%; adjusted odds ratio [aOR] 1.35, 95% CI 0.96-1.90). After adjustment for mode of delivery, prolonged second stage was also not associated with subsequent sPTB in those who delivered by spontaneous and operative vaginal delivery. Those delivered by second-stage caesarean section in the first delivery had a higher risk of sPTB in the second delivery (25/526, 4.8%; aOR 2.66, 95% CI 1.71-4.12; p < 0.001), with a more pronounced risk in those with secondstage caesarean following a prolonged second stage of labour (15/259, 5.8%; aOR 3.40, 95% CI 1.94-5.94; p < 0.001). Conclusion:Second-stage duration in a first term vaginal delivery is not associated with subsequent sPTB. The risk of sPTB is increased following second-stage caesarean section, particularly if performed after a prolonged second stage.

Fetal station at caesarean section and risk of subsequent preterm birth - A cohort study

“…Our findings correspond to those of prior studies reporting an increased risk of PTB after a second-stage CS [17,19,[12][13][14][15]. In a cohort study including 16,340 women, Williams et al found an increased risk of spontaneous PTB after second-stage CS, and an association between prelabor or first-stage CS and subsequent medically indicated PTB [12].…”

“…In contrast, a retrospective cohort study reported a higher risk of PTB after CS than after instrumental vaginal birth [18], indicating that the surgical procedure is relevant. This is supported by results of a large cohort study, published in 2022, showing increased risk after second-stage CS, with no increased risk after a prolonged second stage with vaginal birth [19].…”

“…Two observational studies investigating the duration of the second stage of labor, irrespective of mode of delivery, found no correlation between a prolonged second stage of labor and subsequent PTB [24][25]. In a cohort study by Kleinstern et al, an increased risk of PTB was observed after secondstage CS, but not after a prolonged second stage resulting in vaginal birth [19]. In contrast, Levine et al found that there was an increased risk of spontaneous PTB after a vaginal delivery as well as after a secondstage CS, compared with after a first-stage CS [14].…”

“…Instrumental vaginal delivery might decrease the number of CS performed at a low station. A recently published cohort study concluded that the increased risk of PTB following a prolonged second stage is attributable to women delivered by CS [19]. In the clinical situation, the physician may take appropriate steps to avoid CS at a low station and consider vaginal instrumental delivery.…”