However, the lead study author said adverse outcomes were not associated with mild-to-moderate coronavirus infections.
"Our research shows that serious pregnancy complications appear to occur in women who have severe or critical cases of COVID and not those who have mild or moderate cases," Dr. Torri D. Metz, a maternal-fetal medicine subspecialist and associate professor at the University of Utah Health, said in a related news release.
"This information helps us to counsel our patients more effectively. For pregnant women who have contracted a mild or moderate case of COVID-19, these findings can help to alleviate their fears that they are at an increased risk of having serious pregnancy complications due to the disease."
Findings were presented Thursday at a virtual meeting for the Society for Maternal-Fetal Medicine, according to a news release from the National Institutes of Health, which funded the study.
Researchers from the University of Utah and George Washington University examined records of 1,219 pregnant women from over 30 hospitals across 14 states from March 1 to July 31 who were diagnosed with coronavirus. Nearly half of the patients showed no symptoms, while the other patients faced mild (27%), moderate (14%), severe (8%) and critical (4%) courses of COVID-19 disease.
Older patients with a greater body mass index (BMI) and underlying health conditions tended to develop serious COVID-19. These women faced a higher risk of death and serious birth issues like heavy, abnormal bleeding after birth, C-sections, high blood pressure and preterm delivery.
An abstract of the findings notes four women died due to the novel virus, which exceeds the death rate for expectant women without COVID-19 infection, listed at about 17 deaths for every 100,000 live births.
"High blood pressure and preterm birth also have the potential to cause long-term health problems in women or their infants," reads a related news release.
The study follows previous findings from the Centers for Disease Control and Prevention (CDC), which said pregnant women who contract the coronavirus are more at risk for severe illness and death than non-pregnant women.
The CDC said pregnant women should be counseled about the importance of seeking prompt medical care if they develop symptoms of coronavirus, and that there should be a strong emphasis on coronavirus prevention for pregnant women at each medical appointment.
Fox News' Alexandria Hein contributed to this report.