LAUSR

Objective: The impact of 2021 vaccination and social restriction reversal on preterm birth (PTB) is unclear. We sought to compare the rates of PTB during the COVID pre- and post- vaccination periods with pre-pandemic rate. Study Design: Retrospective cohort comparing all deliveries over 20 weeks at a single tertiary center during ‘early’ COVID (ECOVID 3/2020-6/2020) vs. ‘late’ COVID (LCOVID 3/2021–6/2021), and LCOVID vs. pre-COVID (3-6/2014-2019). PTB < 37weeks, < 34weeks and < 28weeks were compared and stratified by race/ethnicity. Results: There were 20334 deliveries including 2647 ECOVID, 2114 LCOVID and 15574 pre-COVID. We noted 87 (0.03%) and 37 (0.02%) COVID infections in pregnancy during ECOVID and LCOVID, respectively. PTB rate during LCOVID (12.1%) was lower compared to ECOVID (14.5%), p=0.02. Rate of PTB < 34 was also lower during LCOVID (4.4% vs 5.7%, p=0.04). PTB < 28 did not differ (Table1). When controlling for prior PTB, LCOVID was associated with a decreased risk of PTB, adjusted odds ratio (aOR) 0.83[95% confidence interval (CI) 0.70, 0.99]. Among the small number of American Indian patients, PTB increased during LCOVID vs. ECOVID. There were no other significant differences based on race/ethnicity. Overall, PTB rates did not differ in LCOVID vs. pre-COVID. When stratified by race and ethnicity, White individuals had reduced PTB < 37 during LCOVID compared to pre-COVID, aOR 0.70 [95% CI 0.63, 0.99]. PTB rate was unchanged comparing LCOVID vs. pre-COVID in all other racial groups. Among small numbers of Hispanic Puerto Rican patients, PTB rate increased LCOVID vs. pre-COVID (Table 2). Conclusion: During 2021, PTB rates decreased from rates observed in 2020 at the height of COVID restrictions. Among White birthing individuals, PTB decreased in 2021 compared to pre-COVID rates. This decrease was not observed in Black and Hispanic birthing individuals. These data highlight the continued racially disparate impact of the COVID pandemic on PTB rates. [Formula presented] [Formula presented]