THURSDAY, Jan. 2, 2014 (HealthDay News) -- Pregnant women who have a bacterial infection that's diagnosed during hospitalization may be at greater risk of delivering a child with autism, a new study suggests.
These infections -- usually of the genitals, urinary tract or amniotic fluid -- may lead to a nearly 60 percent greater risk of having a child with autism spectrum disorder, the researchers said in a paper published recently in the Journal of Autism and Developmental Disorders.
But, the researchers added, such infections are very common during pregnancy and most don't lead to autism. Half the women included in the study had at least one infection during their pregnancy, regardless of whether their child is autistic. And the study only uncovered an association between bacterial infections and a child with autism -- it did not prove cause-and-effect.
"The vast majority of women who have infections have perfectly healthy babies," said senior study author Lisa Croen, a research scientist with Kaiser Permanente in California. "I don't want women to be overly concerned if they have a cold or are sick during their pregnancy."
The study used Kaiser's extensive medical records to compare the mothers of more than 400 autistic children against the mothers of nearly 2,100 healthy children. The infants were all born between January 1995 and June 1999.
The researchers found no association between infection and autism when looking at all infections that occurred during the pregnancies studied. But they did find an increased risk involving women who had bacterial infections diagnosed during a hospital admission, Croen said.
The researchers said infections diagnosed during a hospitalization might represent more severe infections, which could explain the increased risk of autism.
In particular, infections diagnosed during the second trimester were linked to a threefold increased risk of autism, the study found.
"The second trimester of pregnancy tends to be a very critical time," said Alycia Halladay, senior director of environmental and clinical sciences for Autism Speaks. "Brain structures are starting to develop, and miswiring of the brain can occur at that time."
There are a couple of ways bacterial infection could affect children during gestation, Halladay and Croen said.
The bacteria itself might have some unknown effect, they said. Another possibility is that the mother's immune system might affect the fetus in some way as it fights off the infection.
Halladay said this research underscores the importance of staying healthy and avoiding infections when you are pregnant.
"Wash your hands and stay away from people you know have the flu or some other illness," Halladay said. "These are things that ob-gyns tell you to do anyway. It's consistent with clinical care for women who are pregnant or are of childbearing age and planning to get pregnant."
Women also should make sure to maintain a good relationship with their doctor, Croen said.
"If they aren't feeling well, they should consult their doctor about the best way to take care of themselves so they can have the healthiest pregnancy," she said.
Visit the U.S. National Institute of Mental Health for more on autism.