Post-pandemic structural shifts in perinatal characteristics and outcomes

Abstract Objectives The long-term impact of the COVID-19 pandemic on perinatal outcomes remains understudied in South Korea. We aimed to evaluate nationwide changes in neonatal birth outcomes following pandemic onset. Methods All live births between 2016 and 2023 were analyzed, sourced from Statistics Korea. Bayesian structural time series modeling was used to compare perinatal outcomes after March 2020 with projected trends, adjusting for time-varying sociodemographic covariates and seasonality. Results Overall, 2,347,662 births were included in the analysis (1,413,409 pre-pandemic and 934,253 post-pandemic). After pandemic onset, the proportion of mothers aged ≥35 years and preterm births increased, whereas mean gestational age and birth weight decreased. Bayesian modeling revealed that mean gestational age and birth weight were significantly lower than counterfactual projections. Preterm and extremely preterm births increased by 9.3 % and 15 %, respectively. Mean birth weight z-scores were lower than projected, and the proportion of large-for-gestational-age infants decreased by 10 %. Conclusions These findings suggest that the COVID-19 pandemic has had a sustained and long-term impact on perinatal characteristics at the population-level. Beyond the biological effects of COVID-19 infection, the pandemic may have functioned as a broader social determinant of perinatal health, amplifying existing socioeconomic inequalities and contributing to persistent increases in preterm birth.