Does The Length Of Second Stage Of Labour Or Second Stage Caesarean Section In Nulliparous Women Increase The Risk Of Preterm Birth In Subsequent Pregnancies?

Objectives: This study aimed to investigate the role of prolonged second stage of labour and second stage caesarean section on the risk of spontaneous preterm birth (sPTB) in a subsequent pregnancy.Methods: This was a retrospective cohort study of nulliparous women with two consecutive singleton deliveries between 2014 and 2017 at a tertiary centre. In the vaginal delivery cohort, subsequent pregnancy outcomes for women with a prolonged second stage (>2 h) were compared with those with a normal second stage (<= 2 h). In the caesarean delivery cohort, women with a first stage or a second stage were compared with the vaginal delivery cohort. The primary outcome was subsequent sPTB.Results: A total of 821 women met inclusion criteria, of which 74.8% (614/821) delivered vaginally and 25.2% (207/ 821) delivered by caesarean section. There was no association between a prolonged second stage in the index pregnancy and subsequent sPTB (aOR 0.70, 95% CI 0.13-3.83, p=0.7). The risk of subsequent sPTB was threefold for those with a second stage caesarean section; however this did not reach statistical significance.Conclusions: A prolonged second stage of labour in the index pregnancy is not associated with an increased risk of subsequent sPTB. A second stage caesarean section in the index pregnancy may be associated with an increased risk of subsequent sPTB, however there was no statistically significant difference. These findings are important for counseling and suggest that the effects of these factors are not clinically significant to justify additional interventions in the subsequent pregnancy.