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Boys may be prone to fetal brain development from COVID

AILSA CHANG, HOST:

The country's tally of COVID-19 cases includes more than 200,000 people who were pregnant when they got infected. Now scientists are reporting that boys from those pregnancies may be prone to subtle delays in brain development. Here's NPR's Jon Hamilton.

JON HAMILTON, BYLINE: Before COVID-19 came along, researchers at Massachusetts General Hospital were looking at lots of factors that might affect brain development during pregnancy. Dr. Andrea Edlow says these factors included diabetes, obesity, high blood pressure and even common infections like influenza.

ANDREA EDLOW: When the COVID pandemic started, we pivoted to try to look at fetal brain development and how it might be impacted by maternal SARS-CoV-2 infection.

HAMILTON: The latest result of that pivot is a study of more than 18,000 infants born at eight hospitals in eastern Massachusetts. About 900 of these babies were born to mothers who contracted COVID while pregnant. Edlow says an analysis of electronic health records found one clear difference.

EDLOW: If a mom had SARS-CoV-2 infection in pregnancy and had a male child, her 12-month-old was 94% more likely to have any neurodevelopmental diagnosis.

HAMILTON: In other words, 1-year-old boys from these moms were about twice as likely to have subtle delays in brain development. There was no difference in girls. Edlow says the finding, published in March in the journal JAMA Network Open, is just the latest example of a well-documented sex difference.

EDLOW: Male fetuses and male fetal brain development are known to be more vulnerable to maternal infectious exposures during pregnancy.

HAMILTON: For some reason, the brain of a male fetus is more likely to be affected when a mother's immune system responds to an infection. In the study, this meant boys were more likely to have delays in areas like grasping objects or using language. Those delays can be associated with autism spectrum disorder. But Dr. Roy Perlis says it's hard to make that diagnosis in kids this young.

ROY PERLIS: All we can hope to detect at this point are more subtle sorts of things like delays in language and speech and delays in motor milestones.

HAMILTON: Perlis says some boys may catch up as they get older.

PERLIS: I hope these effects go away. You know, I would be far happier if, at the two-year and the three-year follow-up, there's no effect.

HAMILTON: But Perlis says even if some of the kids turn out to have autism, the overall risk is still quite low.

PERLIS: Most children of moms who have COVID during pregnancy won't have neurodevelopmental consequences even if there is some increase in risk.

HAMILTON: COVID-19 is just the latest maternal infection linked to changes in brain development. Influenza, for example, has been tied to a child's risk for both autism and schizophrenia. Kim McAllister, who directs the Center for Neuroscience at the University of California Davis, says the reason appears to involve certain proteins called cytokines, which regulate the immune system.

KIM MCALLISTER: These are cytokines that are really important for that initial immune response. They make you feel really bad. Some of the cytokines can actually cause fever, and that's a good thing because that's your immune system fighting off the pathogen.

HAMILTON: But these cytokines also may affect the placenta and even reach the fetus. McAllister says scientists are just beginning to understand how this may alter a developing brain.

MCALLISTER: There's no doubt from the animal models that there is a link between maternal immune activation, changes in gene expression in the brain, changes in brain development and long-lasting changes in behaviors.

HAMILTON: Like language delays and difficulty with social interactions. McAllister says the next step is to figure out why this immune activation affects some fetuses but not others.

MCALLISTER: We know that most pregnancies are resilient, but we don't know why. And we don't know why some pregnancies are susceptible.

HAMILTON: When they do know, she says, it may be possible to keep a mom's infection from harming a fetal brain. Jon Hamilton, NPR News. Transcript provided by NPR, Copyright NPR.

Jon Hamilton is a correspondent for NPR's Science Desk. Currently he focuses on neuroscience and health risks.