Pregnancy Outcomes Before and After the Emergence of the SARS-CoV-2 B.1.1.529 (Omicron) Variant [ID: 1365953

Abstract

INTRODUCTION: Starting December 15, 2021, the SARS-CoV-2 B.1.1.529 (Omicron) variant became the predominant strain in the United States. Preliminary data suggest that the Omicron variant causes less severe COVID-19 than earlier variants. We hypothesize that adverse maternal and neonatal outcomes are less likely if infection occurred during the Omicron epoch compared to pre-Omicron. METHODS: This IRB-approved retrospective cohort study was conducted at a major university health system in Maryland from March 2020 to May 2022. We identified patients who were SARS-CoV-2 positive before and after December 15, 2021. Demographics and maternal, obstetric, and neonatal outcomes were collected and compared. Wilcoxon rank-sum and Fisher’s exact tests were used to compare continuous and categorical data, respectively. Adjusted odds ratios (aORs) were calculated using vaccination status. RESULTS: A total of 742 SARS-CoV-2–positive pregnant patients were identified. Of those, 548 (74%) tested positive pre-Omicron and 194 (26%) tested positive during the Omicron wave. Tobacco and illicit drug use were higher among patients in the Omicron epoch. Patients were also older and more likely to have received at least one vaccine dose (3% versus 35%, P<.001). Omicron epoch patients had less severe disease as evidenced by higher rates of asymptomatic infection (72% versus 44%) as well as lower rates of hospital admission due to COVID-19, supplemental oxygenation, and intensive care unit (ICU) admission. However, the odds of ICU admission were not significantly decreased in Omicron epoch patients after adjusting for vaccination (aOR 0.15, 95% CI 0.02–1.14). The odds of preeclampsia and preterm birth less than 34 weeks were lower in Omicron epoch patients after adjusting for vaccination (aOR, 0.61 and 0.38, respectively). Neonatal outcomes were not statistically different between the two groups. CONCLUSION: Pregnant patients infected with SARS-CoV-2 during the Omicron epoch have a less severe disease course than those infected pre-Omicron. Lower ICU admissions during the Omicron epoch may be due to higher vaccination rates.