Risk of Maternal Morbidity Differs by COVID-19 Variant

COVID-19 infection is known to cause adverse outcomes for expecting mothers and their newborns. A recent JAMA study examined whether this association between COVID-19 and severe maternal morbidity was affected by COVID-19 strain.

The retrospective cohort study was conducted in a large US health system between March 2020 and January 2022. The investigators defined 4 distinct periods of the pandemic, as characterized by the COVID-19 viral strain that was predominant.

The wild-type strain period ran from March-December 2020, Alpha (B.1.1.7) from January-June 2021, Delta (B.1.617.2) from July-November 2021, and Omicron (B.1.1.529) from December 2021-January 2022.

The primary study outcome was any event of severe maternal morbidity, which the US Centers for Disease Control and Prevention (CDC) defines as occurring during hospitalization for delivery. Secondary outcomes were number of severe maternal morbidity (SMM) events, respiratory SMM, non-respiratory SMM, and non-transfusion SMM events.

The average age of the 3129 COVID-19 patients was 29.1 years. They were propensity matched with 12504 non-COVID-19 patients that averaged 29.2 years. Data were analyzed from October 2021-June 2022.

The patients with COVID-19 had significantly higher rates of severe maternal morbidity events in all pandemic periods, except for the Omicron period. The risk of any COVID-19-associated SMM increased 2.74% for the wild-type strain, and 2.57% for the Alpha variant, but SMM risk jumped 7.69% higher during the Delta period. These findings were similar across respiratory complications, non-respiratory complications, and non-transfusion outcomes.

The investigators found that the risk of severe maternal morbidity was highest during the period when the Delta COVID-19 variant was predominant. These results are not necessarily surprising, as Delta is known to have caused more severe disease than other variants in all populations.

The observed differences in maternal morbidity by COVID-19 strain emphasize the importance of utilizing vaccines to prevent COVID-19 in expecting mothers. Additionally, COVID-19 infection should be considered a risk factor for adverse peripartum outcomes.