Abstract
Full dilatation caesarean sections (CS) have increased risk of uterine extensions, which leads to cervical trauma that has been associated with an increased risk of spontaneous preterm birth (sPTB) in a subsequent pregnancy. The aim of this study was to determine if CS at full dilatation increased the risk of sPTB in a subsequent pregnancy in our unit. A historical cohort study was performed on women delivered by emergency CS between 2008-2015 (n = 5808) in a university hospital who had a subsequent pregnancy in this time frame (n = 1557). Women were classified into two exposure groups; those who were 6-9 cm and those fully dilated at index CS. The reference group was CS at 0-5 cm dilated. The primary outcome was sPTB < 37 weeks' gestation. CS at 6-9 cm or fully dilated did not significantly increase the odds of sPTB in a subsequent pregnancy (aOR 1.64, 95% CI: 0.83-3.28, p = 0.158; aOR 1.86, 95% CI: 0.91-3.83; p = 0.090, respectively). However, a short interpregnancy interval of <1 year significantly increased the odds of sPTB in a subsequent pregnancy (aOR 3.10, 95% CI: 1.71-5.61). This study has found a short interpregnancy interval following a CS conferred a higher risk of sPTB than full dilatation CS. This finding highlights postnatal contraception and increased surveillance of women with short interpregnancy interval post CS as possible interventions to reduce sPTB.