What is the reason for the decrease in the incidence of preterm births during the COVID-19 pandemic?

Abstract

Introduction: A decrease in preterm births was observed during the COVID-2019 pandemic. The reason for this reduction is not fully understood.

Objective: To determine the causes of the decrease in prematurity during the mandatory isolation period in a university hospital in Córdoba, Argentina, and to test the hypothesis that the decrease in prematurity was due to a reduction in iatrogenic births.

Methods: Two-period retrospective cohort study. Study period between 03/20/2020 and 12/31/2020. Control period between 03/20/2019 and 12/31/2019. Singleton pregnancies delivered at 24 weeks gestational age or older were eligible. Dependent variable: gestational age at delivery. Independent variables: maternal age, birth weight, elective cesarean section, chorioamnionitis, diabetes, pre- eclampsia, parity, education, employment, smoking. A descriptive and comparative bivariate analysis of the data was performed according to their distribution. Significant variables were entered into a multiple linear regression model (MLM) to determine associations. Significance was set at p < 0.05.

Results: A total of 1920 women were included, 946 in the study group and 974 in the control group. Twin pregnancies, congenital infections, women with COVID-19, genetic diseases, congenital malformations, and pregnancies terminated by spontaneous abortion or stillbirth were excluded. Significant differences were found for gestational age at birth, prematurity rate, maternal weight gain, diabetes, pre-eclampsia, employment, elective cesarean section, and smoking. In the MLR model, the increase in maternal weight gain and the decrease in elective cesarean section were significant (coefficient 0.05 ± 0.02; p <0.00 and coefficient -0.33 ± 0.16; p 0.04, respectively).

Conclusion: Gestational age at birth increased significantly during the isolation period, apparently driven by a decrease in the elective cesarean section rate associated with greater maternal weight gain during pregnancy.