Preterm birth (PTB) is the leading cause of infant mortality worldwide. Changes in
PTB rates, ranging from −90% to +30%, were reported in many countries following early
COVID-19 pandemic response measures (‘lockdowns’). It is unclear whether this variation
reflects real differences in lockdown impacts, or perhaps differences in stillbirth
rates and/or study designs. Here we present interrupted time series and meta-analyses
using harmonized data from 52 million births in 26 countries, 18 of which had representative
population-based data, with overall PTB rates ranging from 6% to 12% and stillbirth
ranging from 2.5 to 10.5 per 1,000 births. We show small reductions in PTB in the
first (odds ratio 0.96, 95% confidence interval 0.95–0.98, P value <0.0001), second
(0.96, 0.92–0.99, 0.03) and third (0.97, 0.94–1.00, 0.09) months of lockdown, but
not in the fourth month of lockdown (0.99, 0.96–1.01, 0.34), although there were some
between-country differences after the first month. For high-income countries in this
study, we did not observe an association between lockdown and stillbirths in the second
(1.00, 0.88–1.14, 0.98), third (0.99, 0.88–1.12, 0.89) and fourth (1.01, 0.87–1.18,
0.86) months of lockdown, although we have imprecise estimates due to stillbirths
being a relatively rare event. We did, however, find evidence of increased risk of
stillbirth in the first month of lockdown in high-income countries (1.14, 1.02–1.29,
0.02) and, in Brazil, we found evidence for an association between lockdown and stillbirth
in the second (1.09, 1.03–1.15, 0.002), third (1.10, 1.03–1.17, 0.003) and fourth
(1.12, 1.05–1.19, <0.001) months of lockdown. With an estimated 14.8 million PTB annually
worldwide, the modest reductions observed during early pandemic lockdowns translate
into large numbers of PTB averted globally and warrant further research into causal
pathways.
