Similar findings in Washington
In the Washington study, among 240 pregnant patients with confirmed COVID-19 infection between March 1 and July 30, 2020, 1 in 11 developed severe or critical disease, and 1 in 10 were hospitalized. The pregnant patients had more than triple the risk of hospitalization compared with adults of similar ages in the general population (10% vs. 2.8%; rate ratio, 3.5). Similar to the multistate NICHD study, women were more likely to be hospitalized if they had asthma, hypertension, type 2 diabetes, autoimmune disease, or class III obesity.
Three mothers died of COVID-19, resulting in a case fatality rate 13.6 times greater than nonpregnant patients with COVID-19 in the general population. The absolute difference in the rate was 1.2%. As seen in the NICHD study, preterm birth was more common in mothers with severe or critical COVID-19. Nearly half (45.4%) of mothers with severe or critical COVID-19 delivered preterm compared to 5.2% in those with mild COVID-19 (P < .001).
“Our finding that deaths in pregnant patients contributed disproportionately to deaths from COVID-19 among 20- to 39-year-olds in Washington state is similar to what was observed during the influenza A virus H1N1 2009 pandemic,” Erica M. Lokken, PhD, MS, of the departments of global health and ob.gyn. at the University of Washington, Seattle, and colleagues wrote in the Washington study. But they noted that it took 8 months into the pandemic before pregnant patients were identified as a high-risk group for COVID-19.
“Given the similarity in clinical course between COVID-19 and IAV H1N1 2009 with an increased risk for mortality during pregnancy and the postpartum period, we strongly recommend that pregnant patients should be considered a high-risk population to novel highly pathogenic respiratory viruses until proven otherwise by population-based studies with good ascertainment of pregnancy status,” they wrote.
Judette Louis, MD, MPH, associate professor of ob.gyn. and department chair at the University of South Florida, Tampa, said in an interview that the findings in these studies were fairly expected, but it’s important to have data from such a large cohort as the one presented at SMFM.
“It confirmed that those who had severe disease were more likely to have chronic medical conditions, mirroring what we saw in the general population who isn’t pregnant,” Dr. Louis said. “I thought this was very crucial because as pregnant women are trying to decide whether they should get the COVID vaccine, this provides support to say that if you’re pregnant, you’re more likely to have severe disease [if you have] other chronic medical conditions.”
The findings also confirm the importance of pregnant people taking precautions to avoid infection.
“Even though these individuals are, as a group, in an age cohort that mostly has asymptomatic disease, for some of them, it results in severe disease and even maternal death,” she said. “They should still take it seriously if they’re pregnant.”
The SMFM abstract study was funded by the NICHD. The Washington study was funded by the University of Washington Population Health Initiative, the National Institutes of Health, and philanthropic gift funds. One coauthor of the Washington study is on a Pfizer and GlaxoSmithKline advisory board for immunizations. No other authors or individuals interviewed reported any disclosures.