11 Impact of the coronavirus pandemic lockdown on obstetric outcomes.

Objective: It has been suggested that lockdown during the COVID-19 pandemic decreased prematurity rates. We investigated the impact of lockdown on obstetric outcomes. Study Design: We performed a cohort study on women who gave birth at three maternity hospitals in metropolitan Melbourne, Australia, between Jan 1st, 2019 and Sept 16th, 2020. Data were extracted from the common birth registry of the three maternities. The second lockdown started July 8th, 2020 and required people to stay at home, with limited exemptions. We performed interrupted time-series analysis to compare the monthly rates of preterm birth before 34 weeks prior to and after July 2020. We also compared the group of women who delivered between July and September 2020 to the group of women who delivered during the same period in 2019. Result(s): A total 15,394 women gave birth. Interrupted time-series analysis demonstrated a significantly lower monthly rate of deliveries before 34 weeks of gestational age after July 2020 (Figure 1; p = 0.001). There were 2,207 deliveries between July to Sept. 2019 and 1,870 deliveries between July to Sept. 2020. Baseline characteristics were comparable, except for a significantly difference in twins (1.5% in 2020 versus 2.6% in 2019, p = 0.012). After excluding women with pregnancies complicated by major fetal abnormalities or stillbirth, the risk of preterm delivery before 34 weeks was much lower in patients who delivered between July and September 2020 (2.1% versus 3.3%, RR 0.64, 95% CI 0.44 to 0.94, p = 0.022) (Table 1). Similar patterns were observed for iatrogenic and spontaneous preterm birth at different gestational ages. The effect persisted after logistic regression adjustment for multiple pregnancies (adjusted OR 0.65, 95% CI 0.46 to 0.96, p = 0.028). The decrease in prematurity was not at the cost of an increase in stillbirth or undetected small for gestational age neonates. Conclusion(s): Strict lockdown has a strong impact on iatrogenic and spontaneous