SARS‐CoV‐2
 infection during pregnancy and preterm birth in Massachusetts from March 2020 through March 2021

Background Objectives Methods Results Conclusions SARS‐CoV‐2 infection during pregnancy has been linked to preterm birth, but this association is not well understood.To examine the association between SARS‐CoV‐2 infection and spontaneous and provider‐initiated preterm birth (PTB), and how timing of infection, and race/ethnicity as a marker of structural inequality, may modify this association.We conducted a retrospective cohort study among pregnant people who delivered singleton, liveborn infants (22–44 weeks gestation) from 1 March 2020 to 31 March 2021 (n = 68,288). We used Cox proportional hazards models to compare the hazard of PTB between pregnant people with and without laboratory‐confirmed SARS‐CoV‐2 infection during pregnancy. We evaluated this association according to the trimester of infection, timing from infection to birth, and timing of PTB. We also examined the joint associations of SARS‐CoV‐2 infection and race/ethnicity with PTB using the relative excess risk due to interaction (RERI).Positive SARS‐CoV‐2 tests were identified for 2195 pregnant people (3.2%). The prevalence of PTB was 7.2% (3.8% spontaneous, 3.6% provider‐initiated). SARS‐CoV‐2 infection during pregnancy was associated with an increased risk of PTB overall (adjusted hazard ratio [HR] 1.53, 95% confidence interval [CI] 1.34, 1.74), and provider‐initiated PTB (HR 1.79, 95% CI 1.50, 2.12) but not spontaneous PTB (HR 1.09, 95% CI 0.89, 1.36). Second trimester infections were associated with an increased risk of provider‐initiated PTB, and third trimester infections were associated with an increased risk of both PTB subtypes. A joint inverse association between White non‐Hispanic race/ethnicity and SARS‐CoV‐2 infection and spontaneous PTB (HR 0.56, 95% CI 0.34, 0.94;RERI −0.6, 95% CI −1.0, −0.2) was also observed.SARS‐CoV‐2 infections were primarily associated with an increased risk for provider‐initiated PTB in this study. These findings highlight the importance of promoting infection‐prevention strategies among pregnant people. [ FROM AUTHOR]