Maternal SARS-CoV-2 infection during pregnancy was not associated with an increased risk of congenital anomalies in newborns, according to a large population-based study published last week in JAMA Network Open.
Some initial studies had raised concerns about maternal COVID infection and birth defects, specifically heart abnormalities, while other research has shown no connection.
No increased risk across trimesters
For the new study, researchers led by a team at the University of Toronto analyzed 5,049 live births involving laboratory-confirmed maternal COVID infection and matched them to 20,196 live births without maternal infection from December 2020 through December 2021.
The team found that congenital anomalies occurred in 3.2% of infants born to COVID-infected mothers, compared with 3.1% of those born to uninfected mothers. That translated to 32.5 anomalies per 1,000 live births versus 31.1 anomalies per 1,000 live births, a difference that was not statistically significant.
The rate of abnormalities was similar regardless of when infection occurred during pregnancy. COVID infection during the first trimester was associated with 34.9 congenital anomalies per 1,000 live births, while no infection during the first trimester was associated with 31.8 anomalies per 1,000 live births. This, too, was a nonsignificant difference. There were also no statistically significant differences in incidence rates between groups in the second or third trimesters.
Cardiac defect rates low in both groups
When the team looked specifically at the connection between congenital heart defects and COVID infection, they found that cardiac anomaly rates were slightly higher in newborns with maternal COVID exposure during pregnancy—10.7 versus 8.8 per 1,000 live births—but, again, the difference was not statistically significant.
When COVID infection happened in the first trimester, the rate of cardiac anomalies was 14.1 per 1,000 live births, compared with 8.0 per 1,000 in pregnancies without a first-trimester exposure. While the incidence estimate for first-trimester exposure was slightly higher, the difference again did not reach statistical significance.
“Noncritical cardiac defects represented the largest category of congenital anomalies in this study,” write the researchers. “However, these numbers were low overall in both groups. Following multivariable adjustment, there remained no association between maternal SARS-CoV-2 infection and neonatal cardiac anomalies.”
Findings may provide reassurance
The researchers noted some demographic differences between pregnant women with COVID infection and those without. “Compared with patients without infection, those with infection were more likely to be immigrants and to have high levels of material deprivation and were less likely to receive COVID-19 vaccination and live in rural areas,” they write. Adjusting for those factors, however, did not alter the results.
While the authors say more research on first-trimester infection and the risks of specific anomalies is warranted, they conclude that the findings may provide reassurance to pregnant patients and their healthcare providers.
