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“We already knew that pregnant people are at higher risk for the complications of COVID-19 itself,” says Torri D. Metz, MD, MS, a maternal-fetal medicine  specialist and associate professor of obstetrics and gynecology at U of U ������ο��Ƶ who led the multi-center effort. “Our research is among the first to find that infection with SARS-CoV-2 can elevate the risk of serious consequences related to progression of common pregnancy complications such as developing high blood pressure, having postpartum bleeding, or acquiring an infection other than SARS. This is why we need to make sure pregnant individuals are vaccinated.”

The study appears in the February 7, 2022, issue of

The researchers analyzed electronic medical records of 14,104 pregnant individuals treated at 17 medical centers nationwide that participate in the between March 1, 2020, and December 31, 2020.

About 2,350 of these individuals tested positive for SARS-CoV-2 during pregnancy or within six weeks of delivery. More than 13% of those who tested positive developed pregnancy complications during the study compared to 9% of those who tested negative. All five of the maternal deaths occurred in the SARS-CoV-2 positive group. In addition, the researchers found that:

Complications were more prevalent with moderate to severe COVID-19.

Compared to those who had mild (flu-like) symptoms or were asymptomatic, pregnant individuals who had moderate or severe symptoms, requiring treatment with supplemental oxygen or ICU care, were about three times (26.1% vs. 9.2%) more likely to have serious pregnancy complications.

These problems included eclampsia, severe high blood pressure, kidney failure and other end organ damage caused by high blood pressure, sepsis from infections other than SARS-CoV-2, and endometritis requiring prolonged administration of intravenous antibiotics.

Premature birth was more likely in infected individuals.

SARS-CoV-2 infection was significantly associated with premature birth and NICU admission. However, maternal SARS-CoV-2 was not associated with any other adverse outcomes among newborns. In fact, only 1.2% of newborns tested positive for the virus before discharge.

People with certain characteristics were more likely to have complications.

Individuals who tested positive and subsequently developed pregnancy complications were more likely to have a body mass index (BMI) of 30 or higher and identify as Hispanic or Black. These findings are consistent with other demographic findings among non-pregnant individuals infected with the virus, Metz says.

Pregnant individuals who had moderate or severe COVID-19 symptoms were also at significantly higher risk of cesarean birth (45.4% vs. 32.4%) than those without SARS-CoV-2. However, cesarean birth rates were similar among those who had mild symptoms or were asymptomatic compared with those without SARS-CoV-2.

“Some pregnant individuals who have COVID-19 are just too sick for us to attempt a vaginal birth,” Metz says. “In certain circumstances, such as the onset of preeclampsia, the fetus is also far less likely to tolerate it.”

Among the study’s limitations is that 80% of the SARS-CoV-2 infections were detected in the third trimester, hampering efforts to evaluate the effects of the virus on complications early in pregnancy. 

The study was also conducted prior to the widespread availability of mRNA vaccines. However, Metz says, the new findings bolster the scientific rationale behind efforts to get individuals who are pregnant, or considering having a ������ο��Ƶ, vaccinated.

“The complications of pregnancy we observed were mostly in people who had moderate to severe symptoms of COVID-19,” Metz says. “We know from other studies that vaccination prevents the most severe symptoms of the disease. So, this is just another piece of the puzzle that should encourage pregnant people to get vaccinated.”

Check out this Q & A video with Torri Metz, the study's principal investigator.