Nov. 2 (UPI) -- Pregnant women infected with COVID-19 are about 25% more likely to deliver their babies preterm, according to data released Monday by the U.S. Centers for Disease Control and Prevention.
About 13% of babies born to mothers with the disease were delivered preterm, or at less than 37 weeks, the data showed.
Just over 10% of babies in the United States are born preterm, according to the CDC.
"The proportion of preterm live births among women with [COVID-19] infection during pregnancy was higher than that in the general population in 2019, suggesting that pregnant women with [the disease] infection might be at risk for preterm delivery," agency researchers wrote.
Still, the findings are "preliminary and describe primarily women with second and third trimester infection, and ... subject to change pending completion of pregnancy for all women in the cohort," they said.
For the analysis, the CDC researchers reviewed data on pregnancy and infant outcomes among 5,252 women with laboratory-confirmed COVID-19 from 15 states and Puerto Rico reported between March 29 and Oct. 14.
Among 3,912 live births with known gestational age, 12.9% were preterm, the agency said.
However, fewer than 3% of infants for whom test results were available had evidence of the virus, and most of them were born to mothers who had been infected within one week of delivery, the agency said.
Among 610 infants with reported test results, 2.6% tested positive for COVID-19, the data showed.
Previous studies have shown that pregnant women are unlikely to pass the disease on to their children.
However, data released by the CDC in June indicated that expecting mothers may be at increased risk for severe illness from the virus.
These concerns appear to have been confirmed in a separate analysis the agency released Monday, which found that pregnant women infected with COVID-19 were more than twice as likely to require treatment in a hospital intensive care unit and nearly three times as likely to need mechanical ventilation than "non-pregnant" women.
However, "the absolute risks for severe outcomes for women were low," according to the CDC.
"Pregnant women were at increased risk for severe COVID-19-associated illness," the CDC researchers said.
"To reduce the risk for severe illness and death from COVID-19, pregnant women should be counseled about the importance of seeking prompt medical care if they have symptom sand measures to prevent [coronavirus] infection should be strongly emphasized for pregnant women and their families," they said.