Impact of COVID-19 pandemic restrictions on pregnancy duration and outcome in Melbourne, Australia.

OBJECTIVE: To investigate the effect of restriction measures implemented to mitigate severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission during the coronavirus disease 2019 (COVID-19) pandemic on pregnancy duration and outcome. METHOD(S): A before-and-after study was conducted with cohort sampling in three maternity hospitals in Melbourne, Australia, including women who were pregnant when restriction measures were in place during the COVID-19 pandemic (estimated conception date between 1 November 2019 and 29 February 2020) and women who were pregnant before the restrictions (estimated conception date between 1 November 2018 and 28 February 2019). The primary outcome was delivery before 34weeks' gestation or stillbirth. The main secondary outcome was a composite of adverse perinatal outcomes. Pregnancy outcomes were compared between women exposed to restriction measures and unexposed controls using the chi-square test and modified Poisson regression models, and duration of pregnancy was compared between the groups using survival analysis. RESULT(S): In total, 3150 women who were exposed to restriction measures during pregnancy and 3175 unexposed controls were included. Preterm birth before 34weeks or stillbirth occurred in 95 (3.0%) exposed pregnancies and in 130 (4.1%) controls (risk ratio (RR), 0.74 (95%CI, 0.57-0.96); P=0.021). Preterm birth before 34weeks occurred in 2.4% of women in the exposed group and in 3.4% of women in the control group (RR, 0.71 (95%CI, 0.53-0.95); P=0.022), without evidence of an increase in the rate of stillbirth in the exposed group (0.7% vs 0.9%; RR, 0.83 (95%CI, 0.48-1.44); P=0.515). Competing-risks regression analysis showed that the effect of the restriction measures on spontaneous preterm birth was stronger and started earlier (subdistribution hazard ratio (HR), 0.81 (95%CI, 0.64-1.03); P=0.087) than the effect on medically indicated preterm birth (subdistribution HR, 0.89 (95%CI, 0.70-1.12); P=0.305). The eff