In 2021, the severe acute respiratory syndrome coronavirus 2 Delta variant rapidly proliferated and became dominant. Some but not all research evidence supports that Delta was associated with increased maternal risk. The purpose of this study was to determine whether Delta was associated with risk for cardiac and respiratory complications in a national sample. Of an estimated 3,495,188 delivery hospitalizations in 2021, 1.8% of pre-Delta deliveries (n = 29,580; January–June) and 2.1% of Delta-period deliveries (n = 37,545; July–December) had a coronavirus disease 2019 (COVID-19) diagnosis. The Delta period was associated with increased adjusted odds of respiratory complications (adjusted odds ratio [aOR] = 1.54, 95% CI: 1.41, 1.69) and cardiac severe maternal morbidity (SMM; aOR = 1.54, 95% CI: 1.40, 1.69). Among deliveries with a COVID-19 diagnosis, the Delta period was associated with a higher incidence of respiratory complications (8.4 vs. 3.7%) and cardiac SMM (8.4 vs. 3.5%; p < 0.01 for both). These findings corroborate prior clinical studies suggesting that the Delta strain was associated with an increased maternal population-level clinical burden.

Key Points

The Delta strain was associated with an increased maternal population-level clinical burden.

The Delta period was associated with an increased risk for cardiac and respiratory complications.

Among deliveries with a COVID-19 diagnosis, the Delta period was associated with increased risk.