TORONTO -- A recent study has found that pregnant people with COVID-19 can develop changes to their immune system that makes them susceptible to inflammation and pregnancy complications.

The study, led by researchers from Ohio and California, was published in the journal Cell Reports Medicine last month. The authors looked at 93 COVID-19 positive mothers and 45 of their infants.

The researchers analyzed more than 1,400 cytokines, which are proteins involved in immune activities, as well as other proteins collected from blood specimens. Blood specimens were taken from the mothers close to their initial diagnosis of COVID-19 as well as through their different stages of pregnancy and delivery. Blood specimens were also taken from the placentas.

“We know that pregnancy increases maternal risk for COVID-19, but relatively little is known about the long-term consequences of in utero exposure for infants,” study author Jae Jung said in a news release.

The researchers found that COVID-19 causes a dysregulated immune response, which leads to an immune system that can overreact or underreact when it's not supposed to.

“Our findings show that COVID-19 infection during pregnancy leads to distinct immune alterations in mothers and babies, highlighting how important it will be for long-term follow-up after pregnancy to catch and hopefully prevent any unforeseen long-term health conditions related to prenatal infection,” said Jung.

Stemming from this immune dysregulation, the pregnant women with severe COVID-19 were found to exhibit increased inflammation compared to participants who had mild symptoms of the disease. The women with severe COVID-19 also had higher levels of a protein called interferon lambda 1 (IFNL1), which may explain the low rate of transmission of the SARS-CoV-2 virus to the baby during pregnancy, also known as vertical transmission, the study states.

“This increase in interferon lambda signalling may help explain why we see relatively little direct transmission of COVID-19 between mother and baby during the period right before or after birth—what we call vertical transmission,” co-author Suan-Sin (Jolin) Foo said in the news release. "More research will be necessary to determine if increased expression of IFNL1 … does in fact block vertical transmission.”

The researchers also found that the pregnant women in the cohort exhibited dysregulated levels of proteins associated with pregnancy complications.

Most of the babies born to the COVID-19 positive mothers in the cohort were born healthy, but there were high rates of some pregnancy complications, such as including preeclampsia. Babies born to mothers with severe COVID-19 were more likely to have low birth weight, respiratory distress and were born preterm.

"Despite the lack of robust evidence for vertical transmission, SARS-CoV-2 infection in pregnancy appears to trigger prenatal immune activation that may lead to adverse maternal and neonatal outcomes," the authors wrote, while stressing the importance of long-term clinical monitoring of infants born through COVID-19 pregnancies.