Population based cohort study about SARS-CoV-2 infection during pregnancy. Asthma and foreign ethnicity were identified as risk factors for infection while obstetric outcomes did not change. Obesity, smoking, infection after gestational age (GA) 22 weeks (GA 22-27 weeks: OR 3.77 [1.16-12.29]; GA 28-36 weeks: Or 4.76 [ 1.60-14.12])
IntroductionAssessing the risk factors for and consequences of infection with SARS-CoV-2 during pregnancy is essential to guide clinical guidelines and care. Previous studies on the influence of SARS-CoV-2 infection in pregnancy have been among hospitalised patients, which may have exaggerated risk estimates of severe outcomes because all cases of SARS-CoV-2 infection in the pregnant population were not included. The objectives of this study were to identify risk factors for and outcomes after SARS-CoV-2 infection in pregnancy independent of severity of infection in a universally tested population, and to identify risk factors for and outcomes after severe infection requiring hospital admission. Material and MethodsThis was a prospective population-based cohort study in Denmark using data from the Danish National Patient Register and Danish Microbiology Database and prospectively registered data from medical records. We included all pregnancies between March 1 and October 31, 2020 and compared women with a positive SARS-CoV-2 test during pregnancy to non-infected pregnant women. Cases of SARS-CoV-2 infection in pregnancy were both identified prospectively and through register linkage to secure that all cases were identified and that cases were pregnant during infection. Main outcome measures were pregnancy, delivery, maternal, and neonatal outcomes. Severe infection was defined as hospital admission due to COVID-19. ResultsAmong 82 682 pregnancies, 418 women had SARS-CoV-2 infection during pregnancy, corresponding to an incidence of 5.1 per 1000 pregnancies, 23 (5.5%) of which required hospital admission due to COVID-19. Risk factors for infection were asthma (OR 2.19 [1.41-3.41]) and being foreign born (OR 2.12 [1.70-2.64]). Risk factors for hospital admission due to COVID-19 included obesity (OR 2.74 [1.00-7.51]), smoking (OR 4.69 [1.58-13.90]), infection after gestational age (GA) 22 weeks (GA 22-27 weeks: OR 3.77 [1.16-12.29]; GA 28-36 weeks: OR 4.76 [1.60-14.12]) and having asthma (OR 4.53 [1.39-14.79]). We found no difference in any obstetric or neonatal outcomes. ConclusionsOnly 1 in 20 women with SARS-CoV-2 infection during pregnancy require admission to hospital due to COVID-19. And severe outcomes of SARS-CoV-2 infection in pregnancy are rare. Key MessagePopulation based cohort study about SARS-CoV-2 infection during pregnancy. Asthma and foreign ethnicity were identified as risk factors for infection while obstetric outcomes did not change. Obesity, smoking, infection after GA 22, and asthma increased the risk of hospital admission.