THE IMPACT OF THE COVID-19 LOCKDOWN ON BIRTH WEIGHT AMONG SINGLETON TERM BIRTHS IN DENMARK

In Denmark, a nationwide COVID-19 lockdown was implemented on March 12, 2020 and eased on April 14, 2020. The COVID-19 lockdown featured reduced prevalence of extremely preterm or extremely low birth weight births. Here we explore the impact of this COVID-19 lockdown on term birth weights in Denmark. We conducted a nationwide register-based cohort study on 27,870 live singleton infants, born at term (weeks 37-41), between March 12 and April 14, 2015-2020, using data from the Danish Neonatal Screening Biobank. Primary outcomes, corrected for confounders, were birth weight, small-for-gestational-age (SGA), and large-for-gestational-age (LGA), comparing the COVID-19 lockdown to the previous five years. Data were analysed using linear regression to assess associations with birth weight. Multinomial logistic regression was used to assess associations with size-for-gestational-age (xGA) categories. Adjusted mean birth weight was significantly increased by 16.9 g (95% CI = 4.1 – 31.3) during the lockdown period. A dip in mean birth weight was found in gestational weeks 37 and 38 balanced by an increase in weeks 40 and 41. The 2020 lockdown period was associated with an increased LGA prevalence (aOR 1.13, 95% CI = 1.05 - 1.21). No significant changes in proportions of xGA groups were found between 2015 and 2019. Conclusion The nationwide COVID-19 lockdown resulted in a small but significant increase in birth weight and proportion of LGA infants, driven by an increase in birth weight in gestational weeks 40 and 41. What is known The COVID-19 lockdown periods have had profound, albeit variable, effects on pregnant women in various countries. Extremely preterm and stillbirth rates were reduced during COVID-19 lockdown/mitigation periods in Denmark What is new During COVID-19 lockdown a moderate, but statistically significant, increase in birth weight was seen. The proportion of large-for-gestational age pregnancies was statistically significantly elevated in the lockdown period.