What is driving the decreased incidence of preterm birth during the coronavirus disease 2019 pandemic?

Abstract

Institutions across the world have observed a decrease in the incidence of preterm births during the coronavirus disease 2019 pandemic. The reason for this reduction remains unknown. We sought to explore potential causes for the decrease in preterm births by exploring the following 3 hypotheses: (1) do women who are more likely to be able to work from home incur less physical/or emotional stress resulting in longer gestation? (2) Does the effect of the coronavirus disease 2019 pandemic on the incidence of preterm births vary by race? (3) Is this change provider driven? Using a retrospective cohort of all singleton deliveries at a single tertiary care center, we compared the deliveries for the period before the coronavirus disease 2019 pandemic (January 1, 2018-January 31, 2020) with those occurring during the pandemic (April 1, 2020-October 27, 2020). Comparisons between the period before and during the pandemic were made using Pearson chi-square or t tests as appropriate. The overall incidence of preterm birth, defined as delivery at <37 weeks' gestation, was analyzed and then further classified into spontaneous or indicated preterm births. The population was then stratified by the following categories: (1) insurance type and neighborhood disadvantage; (2) race; and (3) provider type. The provider type was classified as delivery occurring within an outpatient care facility, a clinic that provides prenatal care to those eligible for medical assistance, or a nonoutpatient care facility. In a population of 17,687 pre-coronavirus disease 2019 deliveries, and 5396 deliveries occurring during the coronavirus disease 2019 pandemic, there was a significant decrease in the overall incidence of preterm births (11.1 vs 10.1%; P=.039). Both spontaneous and indicated preterm deliveries decreased across the entire population. When stratified, decreases in the incidence of spontaneous preterm birth before vs during the coronavirus disease 2019 pandemic were limited to deliveries to women from more advantaged neighborhoods (most advantaged, 4.4 vs 3.8%; least advantaged, 7.2 vs 7.4%), white mothers (white, 5.6 vs 4.7%; black, 6.6 vs 7.1%), and those receiving care from nonoutpatient care providers (nonoutpatient care providers, 5.5 vs 4.8%; outpatient care providers, 6.3 vs 6.7%). The incidence of preterm births has decreased during the coronavirus disease 2019 pandemic. Decreases in the rate of spontaneous preterm births were limited to deliveries to white women, living in more advantaged neighborhoods, and deliveries at nonoutpatient care facilities. The coronavirus disease 2019 response regulations may have benefited women with more indicators of advantage disproportionately more.