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 1st, 2020-March 31st, 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. Logistic 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 extreme 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 (Odds Ratio: 0.90; 95% Confidence Interval, CI: 0.87, 0.93), late PTB (0.91; 0.87, 0.94), very PTB (0.87; 0.84, 0.91), and extreme PTB (0.88; 0.82, 0.94). 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.