Hematologic adaptation to mask-wearing among pregnant women and obstetrical outcome during the COVID-19 pandemic.

OBJECTIVE: We aimed to evaluate the effect of the COVID-19 mask-wearing on hematological laboratory components and obstetrical outcomes among women delivering during the COVID-19 pandemic. METHODS: Laboratory results and obstetrical outcomes of women with singleton gestations, admitted for delivery during the COVID-19 mask-wearing period (4-6/2020) were compared to those delivering during the parallel period in 2019 and to a larger cohort derived from nine pre-pandemic years (3/2011-4/2020). RESULTS: Overall, 1,838 women delivered during the COVID-19 pandemic. Compared with the pre-pandemic period, the mean hemoglobin and fibrinogen levels were significantly higher during the mask-wearing period [12.15±1.1 vs. 11.96±1.2, p<0.001 and 472±103.6 vs. 448±85.1 mg/dL, p<0.001, respectively]. Platelets levels were lower [200±56.0 vs. 206±57.5 K/microL, p<0.001]. The rate of delivery at <34 weeks of gestation was lower during the mask-wearing period [1.1% vs. 2%, OR 0.57 (95% CI 0.37-0.88), p=0.01], while cesarean delivery and postpartum hemorrhage rates were higher [26.7% vs. 24.4%, OR 1.13 (95% CI 1.02-1.25), p=0.022 and 4.1% vs. 2.8%, OR 1.5 (95% CI 1.2-1.8), p=0.001, respectively]. CONCLUSION: A hard-to-ventilate space created by wearing a mask during the COVID-19 era may be the underlying cause of the observed higher hemoglobin level among pregnant women, possibly affecting obstetrical outcomes.