Impact of COVID-19 mitigation measures on the incidence of preterm birth: a national quasi-experimental study (preprint)

ABSTRACT

IntroductionPreterm birth is the leading cause of child mortality globally, with many survivors experiencing long-term adverse consequences. Preliminary evidence suggests that preterm births dropped dramatically following implementation of policy measures aimed at mitigating the impact of the COVID-19 pandemic. MethodsWe undertook a national quasi-experimental difference-in-regression-discontinuity approach to study the impact of the COVID-19 mitigation measures implemented in the Netherlands in a stepwise fashion on 9, 15, and 23 March 2020 on the incidence of preterm birth. We used data from the neonatal dried blood spot screening programme (2010-2020) and cross-validated these against national perinatal registry data. Stratified analyses were conducted according to gestational age subgroups, and sensitivity analyses to assess robustness of the findings. We explored potential effect modification by neighbourhood socio-economic status. ResultsData on 1,599,547 singleton newborns were available, including 56,720 post-implementation births. Consistent reductions in preterm birth were seen across various time windows surrounding implementation of the 9 March COVID-19 mitigation measures: {+/-}2 months (n=531,823) odds ratio 0.77 (95% confidence interval 0.66-0.91), p=0.002; {+/-}3 months (n=796,531) 0.85 (0.73-0.98), p=0.028; {+/-}4 months (n=1,066,872) 0.84 (0.73-0.97), p=0.023. Decreases observed following the 15 March measures were of smaller magnitude and not statistically significant. No changes were observed after 23 March. Preterm birth reductions after 9 March were consistent across gestational age strata and robust in sensitivity analyses. They appeared confined to high-socioeconomic status neighbourhoods, but effect modification was not statistically significant. ConclusionIn this national quasi-experimental study, initial implementation of COVID-19 mitigation measures was associated with a 15-23% drop in preterm births in the following months, in agreement with preliminary observations in other countries. It is now of pivotal importance that integration of comparable data from across the globe is undertaken to further substantiate these findings and start exploring the underlying mechanisms.