Uterine surgery before pregnancy is associated with later preterm birth and stillbirth: a population-based record linkage study

BACKGROUND: In high-income countries, uterine surgery is performed for the management of failed or unplanned pregnancies, for excision of polyps and fibroids, for correction of congenital anomalies, for investigation of subfertility, and to facilitate the use of an intrauterine contraceptive device. Many women undergo at least 1 procedure before their first birth. OBJECTIVE: The study hypothesis was that any uterine surgery requiring dilation of the cervix could weaken the cervix and lead to a higher risk of preterm birth in a later pregnancy, that uterine surgery could leave endometrial scarring which might lead to later impaired placentation and increased risk of stillbirth, and that the strength of association would increase for individuals undergoing repeated surgical procedures. STUDY DESIGN: This was a population-linked data study of all first births in New South Wales, Australia, between 2007 and 2019. Linkage between the New South Wales Admitted Patient Data Collection and the Perinatal Data Collection allowed the assessment of uterine surgery exposure and subsequent obstetrical outcomes for individuals. Logistic regression was used to assess the effect of surgery and the known relevant covariates. RESULTS: There were 520,050 women who had a first birth in New South Wales between 2007 and 2019 and 99,659 uterine surgical procedures performed between 2001 and 2019. Uterine surgery occurred in 14.7% of the population. Uterine surgery before a first birth is associated with both later preterm birth (adjusted odds ratio, 1.51 [95% confidence interval, 1.47-1.55]) and stillbirth (adjusted odds ratio, 1.39 [95% confidence interval, 1.26-1.53]). The associations strengthened with repeated procedures and were most substantial at the earliest gestational age. CONCLUSION: This hypothesis-generating study suggests that uterine surgery before pregnancy should be carefully considered with reference to evidence of benefit and any available medical alternative treatment strategies. Further research is needed to understand potential confounding by indication, as the reason for surgery may independently increase pregnancy risks. Antenatal surveillance for the risk of preterm birth may be considered when surgery is unavoidable.