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.
Highlights
In 2017–2018, 168,946 (28.4%) women in the UK were delivered by caesarean section (CS) [1]
The aim of this study was to determine if full dilatation CS increased the risk of spontaneous preterm birth (sPTB) in a subsequent pregnancy in comparison to CS in the first stage of labour in our unit, accounting for confounding factors known to increase the risk of sPTB
The concept of surgery leading to cervical weakness is supported by the evidence that previous cervical treatments increase the risk of preterm birth (PTB) in subsequent pregnancies, secondary to cervical weakness [11,14]
Summary
In 2017–2018, 168,946 (28.4%) women in the UK were delivered by caesarean section (CS) [1]. CS at full cervical dilatation can lead to significant perinatal and maternal morbidity. Maternal morbidity arises from an increased risk of interoperative trauma [4]. 24% of full dilatation CSs will sustain an extension to the uterine incision, further increasing the risk of maternal morbidity [5]. An extension to the uterine incision at full dilatation CS into the cervix means that the cervix undergoes structural change and remodelling as part of the healing process. This cervical damage and repair could render the cervix weaker, so that it dilates prematurely in a subsequent pregnancy, potentially leading to PTB
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