Reductions in stillbirths and preterm birth in covid-19 vaccinated women: a multi-centre cohort study of vaccine uptake and perinatal outcomes.

Abstract

Background: We aimed to measure COVID-19 vaccine uptake among women giving birth in Melbourne and to compare perinatal outcomes by vaccination status. Method(s): Routinely-collected data from all 12 public maternity hospitals in Melbourne were extracted on births >=20 weeks' from 01.07.21 to 31.03.22. Sociodemographic characteristics and perinatal outcomes were compared between COVID-19 vaccinated and unvaccinated women. The primary outcomes were stillbirth and preterm birth in singletons >24 weeks. We calculated the adjusted odds ratio of perinatal outcomes among vaccinated versus unvaccinated women using inverse propensity score weighting regression adjustment with multiple covariates; P < 0.05 was considered significant. Result(s): Births from 32 536 women were analysed: 17 365 (53.4%) were vaccinated and 15 171 (47.6%) were unvaccinated. Vaccination status was significantly associated with multiple sociodemographic factors. Vaccinated women had a significantly lower rate of stillbirth compared with unvaccinated women (0.2% vs. 0.8%, aOR 0.18, 95% CI 0.09- 0.37, P < 0.001). Vaccination was associated with a significant reduction in total preterm births <37 weeks (5.1% vs. 9.2%, aOR 0.60, 95% CI 0.51-0.71, P < 0.001), spontaneous preterm birth (2.4% vs. 4.0%, aOR 0.73 95% CI 0.56-0.96, P = 0.02) and iatrogenic preterm birth (2.7% vs. 5.2%, aOR 0.52, 95% CI 0.41-0.65, P < 0.001). There was no significant increase in congenital anomalies or foetal growth restriction among vaccinated women. Conclusion(s): COVID-19 vaccination during pregnancy was associated with a reduction in stillbirth and preterm birth, and not associated with any adverse impacts on foetal growth or development. Vaccine coverage was significantly influenced by known social determinants of health.