Amelioration of prevalence of threatened preterm labor during the COVID-19 pandemic: nationwide database analysis in Japan.

We aimed to evaluate the changes in maternal and neonatal complications such as threatened preterm labor (TPL) and preterm birth before and during the coronavirus disease 2019 (COVID-19) pandemic using large-scale real-world data in Japan. We obtained data from the Japan Medical Data Center claims database and evaluated differences in maternal and neonatal complications, such as the prevalence of TPL and preterm birth before the COVID-19 pandemic (in the year 2018 or 2019) and during the COVID-19 pandemic (in 2020). We included 5533, 6257, and 5956 deliveries in the years 2018, 2019, and 2020, respectively. TPL prevalence and preterm birth had significantly decreased in 2020 (41.3%, 2.6%, respectively) compared with those reported in 2018 (45.3%, 3.9%, respectively) and 2019 (44.5%, 3.8%, respectively). Neonatal outcomes such as low-birth-weight infants and retinopathy of prematurity were also improved during the pandemic. There were no clear trends in the prevalence of maternal complications such as hypertensive disorders of pregnancy; hemolysis, elevated liver enzymes, and low platelets (HELLP) syndrome; and preeclampsia. Oral ritodrine hydrochloride usage in all participants had significantly decreased during the COVID-19 pandemic. In conclusion, our results suggest that the COVID-19 pandemic has ameliorated TPL and consequently reduced the number of preterm births.