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

Abstract

Purpose: 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).

Methods: 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.

Results: 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).

Conclusions: 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.

Keywords: COVID-19; Cesarean delivery; Interrupted time series analysis; Preterm birth; Stillbirth.