Pregnancy outcomes in Italy during COVID-19 pandemic: a population-based cohort study.

Objective: To compare the estimates of preterm birth (PTB; 22-36 weeks gestational age, GA) and stillbirth rates during COVID-19 pandemic in Italy with those recorded in the three previous years.

Design: A population-based cohort study of liveborn and stillborn infants was conducted using data from Regional Health Systems and comparing the pandemic period (March 1 , 2020-March 31 , 2021, N= 362,129) to an historical period (January 2017- February 2020, N=1,117,172). The cohort covered 84.3% of the births in Italy.

Methods: Poisson regressions were run in each Region and meta-analyses were performed centrally. We used an interrupted time series regression analysis to study the trend of preterm births from 2017 to 2021.

Main Outcome Measures: The primary outcomes were PTB and stillbirths. Secondary outcomes were late PTB (32-36 weeks' GA), very PTB (<32 weeks' GA), and extremely PTB (<28 weeks' GA), overall and stratified into singleton and multiples.

Results: The pandemic period compared with the historical one was associated with a reduced risk for PTB (Risk Ratio: 0.91; 95% Confidence Interval, CI: 0.88, 0.93), late PTB (0.91; 0.88, 0.94), very PTB (0.88; 0.84, 0.91), and extremely PTB (0.88; 0.82, 0.95). In multiples, point estimates were not very different, but had wider CIs. No association was found for stillbirths (1.01; 0.90, 1.13). A linear decreasing trend in PTB rate was present in the historical period, with a further reduction after the lockdown.

Conclusions: We demonstrated a decrease in PTB rate after the introduction of COVID-19 restriction measures, without an increase in stillbirths.