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 researches 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, Dr. 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. Dr. Metz said the vast majority of preterm deliveries were indicated, but only a small proportion were 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.