Background Preterm birth is the leading cause of child mortality globally, with many survivors experiencing long-term adverse consequences. Preliminary evidence suggests that numbers of preterm births greatly reduced following implementation of policy measures aimed at mitigating the effects of the COVID-19 pandemic. We aimed to study the impact of the COVID-19 mitigation measures implemented in the Netherlands in a stepwise fashion on March 9, March 15, and March 23, 2020, on the incidence of preterm birth.Methods We used a national quasi-experimental difference-in-regression-discontinuity approach. We used data from the neonatal dried blood spot screening programme (2010−20) cross-validated against national perinatal registry data. Stratified analyses were done according to gestational age subgroups, and sensitivity analyses were done to assess robustness of the findings. We explored potential effect modification by neighbourhood socioeconomic status, sex, and small-for-gestational-age status. FindingsData on 1 599 547 singleton neonates were available, including 56 720 births that occurred after implementation of COVID-19 mitigation measures on March 9, 2020. Consistent reductions in the incidence of preterm birth were seen across various time windows surrounding March 9 (± 2 months [n=531 823] odds ratio [OR] 0•77, 95% CI 0•66-0•91, p=0•0026; ± 3 months [n=796 531] OR 0•85, 0•73-0•98, p=0•028; ± 4 months [n=1 066 872] OR 0•84, 0•73-0•97, p=0•023). Decreases in incidence observed following the March 15 measures were of smaller magnitude, but not statistically significant. No changes were observed after March 23. Reductions in the incidence of preterm births after March 9 were consistent across gestational age strata and robust in sensitivity analyses. They appeared confined to neighbourhoods of high socioeconomic status, but effect modification was not statistically significant.Interpretation In this national quasi-experimental study, initial implementation of COVID-19 mitigation measures was associated with a substantial reduction in the incidence of preterm births in the following months, in agreement with preliminary observations elsewhere. Integration of comparable data from across the globe is needed to further substantiate these findings and start exploring underlying mechanisms.

IntroductionHealth inequalities can be observed in early life as unfavourable birth outcomes. Evidence indicates that neighbourhood socioeconomic circumstances influence health. However, studies looking into temporal trends in inequalities in birth outcomes including neighbourhood socioeconomic conditions are scarce. The aim of this work was to study how inequalities in three different key birth outcomes have changed over time across different strata of neighbourhood deprivation.MethodsNationwide time trends ecological study with area-level deprivation in quintiles as exposure. The study population consisted of registered singleton births in the Netherlands 2003–2017 between 24 and 41 weeks of gestation. Outcomes used were perinatal mortality, premature birth and small for gestational age (SGA). Absolute rates for all birth outcomes were calculated per deprivation quintile. Time trends in birth outcomes were examined using logistic regression models. To investigate relative inequalities, rate ratios for all outcomes were calculated per deprivation quintile.ResultsThe prevalence of all unfavourable birth outcomes decreased over time: from 7.2 to 4.1 per 1000 births for perinatal mortality, from 61.8 to 55.6 for premature birth, and from 121.9 to 109.2 for SGA. Inequalities in all birth outcomes have decreased in absolute terms, and the decline was largest in the most deprived quintile. Time trend analyses confirmed the overall decreasing time trends for all outcomes, which were significantly steeper for the most deprived quintile. In relative terms however, inequalities remained fairly constant.ConclusionIn absolute terms, inequalities in birth outcomes by neighbourhood deprivation in the Netherlands decreased between 2003 and 2017. However, relative inequalities remained persistent.

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Introduction Preterm 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. Methods We 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. Results Data on 1,599,549 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. Conclusion In 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.