Data are mean ± standard deviation or number (%)
a Compared to the mask-wearing period
b Composite neonatal outcome consisted of any of the following: stillbirth, neonatal death during first 24 hours, mechanical ventilation during first 24 hours, asphyxia, hypoxic ischemic encephalopathy and neonatal intensive care unit admission.
OR- odds ratio, CI- confidence interval, NICU- neonatal intensive care unit
OR was calculated only for significantly different categorical variables.