Contracting COVID-19 during pregnancy could make a woman’s unborn child more prone to diseases and health issues later on, a new study reveals. Scientists with the National Institutes of Health say mild infections in the mother can permanently damage the immune system of their offspring.

The study adds that this may lead to a host of chronic conditions ranging from asthma and eczema to bowel disease.

“The immune system has evolved in the face of microbial exposure,” writes first author Dr. Ai Ing Lim and researchers in the journal Science.

“How maternal infection experienced at distinct developmental stages shapes the offspring immune system remains poorly understood. Here, we show that during pregnancy, maternally restricted infection can have permanent and tissue-specific impacts on offspring immunity.”

Experiments with mice discovered disease-causing bugs boost a fetus’ immunity to gut infections. However, this happens at the cost of a long-lasting predisposition to inflammatory disorders. The findings adds to evidence the immune system begins developing in the womb and is greatly influenced by the mother’s health.

Pregnancy often has a link to the suppression of the body’s ability to fight diseases. However, it remains unknown how undiagnosed everyday infections influence the child’s immunity. These include mild urinary tract, respiratory, or food-borne infections that often resolve themselves without treatment.

Infections in the mother may lead to poor gut health in infants

In the study, researchers infected pregnant mice with the food poisoning bug Yersinia pseudotuberculosis, which causes a mild and transient illness. The infection was short lived and restricted to the mother. Yet intestinal immune system cells called T helpers were elevated in the offspring into adulthood.

Further analysis revealed the bug fueled a chemical in the mothers called IL-6 (interleukin-6) that causes inflammation in response to infection. It changed the intestinal stem cells of the unborn pups. Dr. Lim adds that while these offspring showed enhanced protective immunity to gut infection, they also exhibited higher susceptibility to intestinal inflammatory disease, like colitis.

“As a result, offspring of previously infected dams develop enhanced protective immunity to gut infection and increased inflammation in the context of colitis,” study authors write in the study. “Thus, maternal infection can be coopted by the fetus to promote long-term, tissue-specific fitness, a phenomenon that may come at the cost of predisposition to inflammatory disorders.”

The findings could shed light on rising cases of allergies and behavioral conditions such as ADHD (attention deficit hyperactivity disorder) and autism.

“The past few decades have seen a marked increase in the incidence of inflammatory disorders in children, including asthma, allergies and behavioral deficits driven in part by neuroinflammation,” researchers write in a media release.

“Future work should address whether and how immune imprinting in utero may underlie the predisposition to inflammatory disorders.”