New research shows that the children of women who contact a severe infection — like the flu, sepsis, or pneumonia — may have a greater risk of  depression and being on the autism spectrum. Minor infections, such as a urinary tract infection, may also increase the risk.

Dr. Kristina Adams Waldorf co-authored the study, and she is a obstetrics and gynecology professor at the University of Washington School of Medicine. She encourages women to get the flu shots, and she wants mothers to be cautious as the infection “can be very dangerous for your baby’s mental health and brain development.”

The Study

Waldorf and the other researchers looked at patient data from Sweden’s health registry “for the entire population of pregnant women that were hospitalized between 1973 and 2014.”

“And then we had up to 41 years of follow-up on those children that stayed in Sweden,” says Waldorf.

The total amount of children records they looked at totaled 1,791,520. Waldorf called the results “very surprising.”

The results showed that when a child is exposed to an infection during utero, there is 79% increased risk of them being born on the autism spectrum and a 24% increased risk of them being diagnosed with depression.  There was also an increased risk of suicide.

There was no increased risk of children developing bipolar disorder or psychosis.

“We need more research into understanding the inflammation that occurs in the urinary tract infection and how it might impact the fetus,” says Waldorf. “The hippocampus is a very vulnerable part of the brain that is targeted by Zika virus infection but may be vulnerable to other infections as well,” she says.

Margaret McCarthy, a University of Maryland School of Medicine professor, calls the study “astonishing.”

“To my knowledge, this is the largest and most comprehensive study of in utero infections and the health outcomes for the offspring,” says McCarthy.

The risk increased regardless of infection type, and this “highlights that there’s something very subtle that can be very profound in brain development, and it probably has to do with sensitive periods in brain development that we don’t understand yet,” she says.

“Brain development is really complicated, and things that we think are relatively benign sometimes aren’t, because we still don’t understand just a lot of the basic signaling molecules that are involved.”

Dr. Alan S. Brown, a Columbia University Medical Center professor of psychiatry, wrote that “overall, the investigators have done a commendable job, [but the] “findings could also be influenced by treatment-seeking behaviors.”

He cited a study from Taiwan that demonstrated the correlation between infection treatments in the third trimester and the autism risk.

“Starting in the 1990s, we demonstrated that prenatal exposure to several pathogens including rubella, influenza and toxoplasmosis are related to risk of schizophrenia. In more recent work, we showed that prenatal influenza was related to bipolar disorder,” he writes.

He praises the new research, and states that the “relationships between prenatal infection and autism and opens up a potential new avenue of exploration regarding prenatal infection and depression.”

McCarthy cautions women not to panic. They should try to avoid infection and treat one quickly if it were to occur.