Clinical characteristics and confounders of the new coronavirus infection in low-risk pregnant women: an analysis of three years of the pandemic: A cross sectional study

Background. During the three years of the new coronavirus infection (NCI) pandemic, young women of low infectious risk made a certain contribution to the severe maternal morbidity and mortality from COVID-19.

Aim. To establish risk factors for morbidity and give a clinical assessment of COVID-19 during epidemic outbreaks in 2020, 2021, and 2022 in low-risk pregnant women.

Materials and methods. The study included three groups of pregnant women with clinically manifested and laboratory-confirmed SARS-CoV-2 infection: 163 pregnant women who became ill in the first wave of the epidemic in October-December 2020, 158 in the second and third epidemic wave in July and October 2021, and 160 in the fourth epidemic wave in January–February 2022. Each comparison group included 100 pregnant women who did not become ill during the same periods of the pandemic. Patients of all groups were in the III trimester of gestation, comparable in age (18–35 years), social status, parity, and body mass index, and had no known risk factors for COVID-19.

Results. Iron-deficiency anemia, tobacco smoking, and belonging to the East Asian ethnic group showed a stable association with the incidence of COVID-19 in low-risk pregnant women. In the first year of the pandemic (strains zero and Alpha), the clinical presentation of NCI was dominated by a loss of smell and/or taste (87.7%), drowsiness (68.7%), and dyspnea even with a mild degree of lung damage (68.1%). The epidemics of the second year of the COVID-19 pandemic (Delta strain) were characterized by a more severe course of the disease than in the first year: fever was more often reported above 38°C (19.6% vs 7.4%; pχ²=0.006), pneumonia confirmed by computed tomography (61.4% vs 21.4%; pχ²<0.001), severe lung damage (CT-3: 11.4% vs 4.9%; pχ²=0.040; CT-4: 0 vs 6.3%; pχ²<0.05), intensive care unit admission (11.4% vs 6.4%; pχ²=0.041); there were cases of invasive mechanical ventilation (1.89% vs 0; pχ²=0.118) and deaths (0.63% vs 0; pχ²=0.492). In the epidemic of the third year of the pandemic (Omicron strain), the COVID-19 clinical presentation was similar to seasonal acute respiratory viral infection: the predominant symptoms included runny nose (66.7%) and cough (54.4%); pneumonia was rare (3.8%).

Conclusion. Iron deficiency anemia, tobacco smoking, and belonging to the East Asian ethnic group are confounders of COVID-19 disease in pregnant women without known infectious risk factors. Unlike the epidemics of the first and third year of the pandemic with dominant zero, Alpha, and Omicron strains, epidemic outbreaks of the second year of COVID-19 caused by the Delta strain were characterized by the most severe disease course, a high rate of pneumonia and deaths even in low-risk patients.