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Pregnant patients with COVID-19 infections were more likely to experience severe disease if they had preexisting comorbidities, such as chronic hypertension, asthma, or pregestational diabetes, according to findings from a new study presented at the meeting sponsored by the Society for Maternal-Fetal Medicine.
The study included outcomes for the largest multistate cohort of pregnant patients with COVID-19 outside of what the Centers for Disease Control and Prevention is tracking. Its findings also mirrored those of a multicenter, retrospective study in Washington state, published in the American Journal of Obstetrics & Gynecology. That study also found that pregnant patients hospitalized for COVID-19 were more likely to have comorbidities, and both studies found an increased likelihood of preterm birth among pregnant patients with severe or critical disease.
Disease Severity Linked to Risk of Perinatal Complications
In the abstract presented at the SMFM meeting, more severe disease was associated with older age and a higher median body mass index, as seen in the general population, but the researchers found no differences in disease severity occurred by race or ethnicity, Torri D. Metz, MD, of the Eunice Kennedy Shriver National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network, told attendees of the conference. The researchers also found that perinatal complications were more prevalent in those with severe or critical COVID-19 disease but not in those with mild or moderate disease. Vertical COVID-19 transmission from mother to child was rare.
The observational study included all patients who had a singleton pregnancy, had a positive SARS-CoV-2 test, and delivered between March 1 and July 31, 2020, at one of the 33 U.S. hospitals in the NICHD Maternal-Fetal Medicine Units Network, spread across 14 states. The researchers used electronic medical records to determine incidence of cesarean delivery, postpartum hemorrhage, hypertensive disorders of pregnancy, preterm birth (less than 37 weeks), maternal death, infant death, and positive infant COVID-19 test. They tracked mothers through 6 weeks post partum and newborns through delivery hospitalization.
Of 1,291 patients in the cohort, 1,219 received their first positive COVID-19 test during pregnancy. The others tested positive while in the hospital for delivery or within a month and a half after discharge. Limiting their analysis to those who developed COVID-19 while pregnant prior to delivery, nearly half (47%) were asymptomatic.
The disease was mild in 27%, moderate in 14%, severe in 8%, and critical in 4%. The researchers used the National Institutes of Health classifications for severity and included deaths in the critical group. The most common symptom was a cough, reported by a third of the patients (34%). Four of six maternal deaths that occurred were caused by COVID-19.
Compared with an average age of 28 in those without symptoms, the mean age was 29 in those with mild/moderate disease and 30 in those with severe/critical disease (P = .006). Similarly, the mean BMI was 28.3 in asymptomatic patients, 29 in those with mild/moderate disease, and 32.3 in those with severe/critical disease (P < .001). Despite a diverse cohort – 53% Hispanic, 23% Black, and 15% White – the researchers found no racial/ethnic trends in disease severity.
Patients who had asthma, chronic obstructive pulmonary disorder, pregestational diabetes, chronic hypertension, chronic liver disease, or a seizure disorder were all significantly more likely to have critical/severe disease than mild/moderate disease, and more likely to have mild/moderate disease than asymptomatic (P values ranged from < .001 to .02).
The mothers with critical or severe illness were 1.6 times more likely to have cesarean births and to have hypertensive disorders of pregnancy, and they were twice as likely to have postpartum hemorrhage (P < .001; P = .007). Those with mild or moderate disease, however, had no increased risks for perinatal complications over asymptomatic patients.
Critical or severe illness was also associated with more than triple the risk of preterm birth (adjusted risk ratio, 3.6; P < .001). Newborns of mothers with critical or severe illness also had three times greater risk of neonatal ICU admission (ARR, 3.1; P <. 001) and weighed an average 385 g less than newborns of asymptomatic mothers. COVID-19 rate among infants was only 1% during delivery hospitalization.
Since the study cutoff was July 30 and COVID infections only became prevalent in March, the researchers were unable to evaluate women for outcomes resulting from COVID infections in early pregnancy, such as congenital anomalies or early miscarriage, Metz said. In addition, since many of the sites are urban centers, the data may not be generalizable to rural areas.
Peter S. Bernstein, MD, MPH, of Montefiore Medical Center, New York, asked whether the increased cesarean deliveries and preterm births in the group of women with severe disease were caused by usual obstetric causes or the treatment of COVID-19 infection. Metz said the vast majority of preterm deliveries were indicated, but only a small proportion was induced for COVID-19 alone. “A lot had hypertensive disorders of pregnancies or PPROM, so it’s partly driven by the infection itself but also partly driven by some of those perinatal complications,” she said.
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 was 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,” 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.
This article originally appeared on MDedge.com, part of the Medscape Professional Network.