Gemmill A, Casey JA, Catalano R, et al. - The data show evidence of unexpected reductions in preterm delivery during the 2020 SARS-CoV-2 pandemic in the United States. The observed decreases below expectation differed by both delivery timing and birth month, implying that different mechanisms, which require additional investigation, may explain these patterns.

• The authors derived nationwide monthly rates (per 100 births) for four perinatal indicators from 2015 to 2020: preterm (< 37 weeks’ gestation), early preterm (< 34 weeks’ gestation), late preterm (34–36 weeks’ gestation), and caesarean delivery.

• Preterm birth rates were observed to be lower than expected for several months during the 2020 pandemic.

• The extent of these decreases was greatest in early and late 2020, with a 5%–6% relative difference between observed and predicted happening between March and November.

• In March 2020, for example, the observed preterm birth rate of 9.8 per 100 live births was lower than the 95% prediction interval of the rate anticipated from history, which was 10.5 preterm births per 100 live births.

• The rate of caesarean deliveries did not differ significantly from expectations.