ABSTRACT
Adverse effects of COVID-19 on perinatal health have been documented, however there is a lack of research that separates individual disease from other changing risks during the pandemic period. We linked California statewide birth and hospital discharge data for 2019-2020, and compared health indicators among 3 groups of pregnancies: [a] 2020 delivery with COVID-19, [b] 2020 delivery with no documented COVID-19, and [c] 2019 pre-pandemic delivery. We aimed to quantify the links between COVID-19 and perinatal health, separating individual COVID-19 disease (a vs b) from the pandemic period (b vs c). We examined the following health indicators: preterm birth, hypertensive disorders of pregnancy, gestational diabetes mellitus and severe maternal morbidity. We applied model based standardization to estimate "average effect of treatment on the treated" risk differences (RD), and adjusted for individual and community-level confounders. Among pregnancies in 2020, those with COVID-19 disease had higher burdens of preterm birth (RD[95% confidence interval (CI)]=2.8%[2.1,3.5]), hypertension (RD[95% CI]=3.3%[2.4,4.1]), and severe maternal morbidity (RD[95% CI]=2.3%[1.9,2.7]) compared with pregnancies without COVID-19 (a vs b) adjusted for confounders. Pregnancies in 2020 without COVID-19 had a lower burden of preterm birth (RD[95% CI]=-0.4%[-0.6,-0.3]), particularly spontaneous preterm, and a higher burden of hypertension (RD[95% CI]=1.0%[0.9,1.2]) and diabetes RD[95%CI]=0.9%[0.8,1.1] compared with pregnancies in 2019 (b vs c) adjusted for confounders. Protective associations of the pandemic period for spontaneous preterm birth may be explained by socioenvironmental and behavioral modifications, while increased maternal conditions may be due to stress and other behavioral changes. To our knowledge, our study is the first to distinguish between individual COVID-19 disease and the pandemic period in connection with perinatal outcomes.