Decreases in preterm birth during the first COVID-19 lockdown in France by gestational age sub-groups and regional COVID-19 incidence

Abstract

Given contradictory evidence about preterm birth (PTB) decreases during COVID-19 lockdowns, we investigate PTB rates during France's strict nationwide lockdown (March 17, 2020 to May 10, 2020). This is an interrupted time series analysis using data on maternal delivery hospitalizations in France from January 01, 2016 to July 31, 2020 (3,448,286 singleton births ≥22 weeks' gestational age (GA)). Outcomes were weekly PTB rates (overall and by GA sub-group: <28, 28-31, 32-34, 35-36 weeks), stillbirth and cesarean birth. We estimate odds ratios (OR) using the lockdown period as exposed and other weeks as unexposed, nationally and for districts grouped by COVID-19 incidence. Of 96,076 singleton live births during the lockdown, 4,799 were preterm. PTB rates were 6% (OR: 0.94, 95% CI: 0.90-0.98) lower than expected over this period. This decrease occurred among births 35-36 weeks' GA (OR: 0.92, 95% CI: 0.87-0.98), with no detectable reductions for other GA groups. Cesarean and stillbirth rates were stable. Larger differences were observed in districts with low (OR: 0.92, 95% CI 0.87-0.98) versus moderate/high COVID-19 incidence (OR: 0.97, 95% CI 0.92-1.03). Late preterm births decreased during France's first lockdown without concurrent change in cesareans and stillbirths. Effects were not more pronounced in moderate/high-COVID-19 districts, contradicting expectations if healthcare disruption were a principal cause.