Preterm birth rates after full-dilatation caesarean section in the first pregnancy: outcomes in contemporary obstetric practice.

BACKGROUND

Spontaneous preterm birth (sPTB) following full dilatation caesarean section (FDCS) has been linked to cervical or lower uterine segment trauma in historical cohorts, but this evidence largely predates modern obstetric practice. This study aimed to determine whether the association persists in a contemporary population, using electronic maternity records from two UK units (BadgerNet, October 2018-February 2026).

RESULTS

Of 11,350 nulliparous women with a term singleton first birth, 3,288 had subsequent pregnancy data available, including 88 (2.7%) who had undergone FDCS. sPTB occurred in 8.0% of women after FDCS, compared with 1.6% after spontaneous vaginal delivery, 0.9% after forceps, 2.7% after ventouse, 0.35% after elective caesarean, and 1.3% after emergency caesarean not at full dilatation. After adjusting for maternal age, BMI, smoking status, and interpregnancy interval, FDCS remained independently associated with sPTB (aOR 7.20, 95% CI 2.91-17.80, p < 0.001). No other mode of delivery, BMI, or smoking status showed a significant independent association.

DISCUSSION: These findings suggest, in a modern obstetric cohort, that the previously reported link between FDCS and subsequent sPTB persists. The strength of association was notable despite adjustment for key confounders, though the small number of events and wide confidence interval limit precision. This observational study does not establish a causal relationship.

CONCLUSION

FDCS in a first pregnancy is associated with a substantially increased risk of sPTB in the subsequent pregnancy. These findings may inform individualised counselling about this risk. This study did not evaluate cervical-length surveillance or preventive interventions. Larger prospective studies are needed to confirm this association and evaluate these approaches.