Liz Szabo -- USA TODAY
A new study finds that pregnant women who have their labor started or sped up artificially are slightly more likely to have autistic children.
The increased autism risk likely stems from an underlying problem with the pregnancy, rather than any of the methods used to jump-start labor, says lead author Simon Gregory of the Duke Institute of Molecular Physiology.
It's possible that "infants destined to develop autism are less likely to send out the correct biochemical signals for normal progression of labor," says Tara Wenger, a pediatric genetics fellow at the Children's Hospital of Philadelphia, who wasn't involved in the new study, published in JAMA Pediatrics.
Pregnancy complications increase the risk of many developmental disorders, says Michael Rosanoff, associate director for public health research and scientific review at Autism Speaks, an advocacy group.
And a growing number of studies now link autism to a variety of things that can compromise the health of a pregnancy, says Rosanoff, who wasn't involved in the study, funded by the Environmental Protection Agency. Researchers are increasingly looking at prenatal risk factors for autism, because this period plays a key role in brain development. Science has ruled out vaccines as a cause of autism, he says.
But studies have found that children are at higher risk for autism if they are born early or very small; if they are in medical distress during delivery; if they have older mothers or fathers; or if they are born less than a year after an older sibling. Autism risk also goes up if a mother has diabetes or high blood pressure; is obese; is exposed to significant air pollution during pregnancy; had low levels of folic acid; takes medications such as an anti-seizure drug called valproic acid; or makes antibodies toxic to the fetal brain.
Gregory notes that his findings are still preliminary and that women shouldn't resist a doctor's recommendation about jump-starting labor out of fear of autism.
Inducing labor can often reduce the risk of stillbirth, such as when a pregnancy lasts more than a week or so beyond the usual 40 weeks, says co-author Chad Grotegut, a Duke maternal-fetal medicine specialist. Augmenting labor, which may be done when natural labor stalls, can reduce the risk of maternal or fetal infections or post-partum hemorrhage.
And while the link between autism and jump-starting labor is consistent with smaller, earlier studies, the research doesn't prove that labor induction or augmentation actually causes autism, Gregory says.
In the new study, researchers analyzed the records of 625,042 North Carolina births, which were linked to school records that noted any diagnosis of autism.
Those records didn't specify where children fell on the autism spectrum, the study says.
Doctors can induce or speed up labor in several ways, such as by applying a hormone gel to the cervix or giving women intravenous oxytocin, an artificial version of a natural hormone involved in labor, Gregory says.
Women whose labor was induced were 13% more likely to have an autistic child, compared to women whose labor wasn't induced. Women whose labor was sped up were 16% more likely to have a child later diagnosed with autism, the study found. Those whose labor was both induced and augmented were 27% more likely to have an autistic child.
In comparison, the risk of autism went up 23% when the mother had diabetes, and 25% when the fetus was in distress, the study says.
There was no increase in autism risk among women who had C-sections, Gregory says.
He says scientists should look more closely at labor induction with oxytocin. Oxytocin, sometimes called the "love hormone," plays a key role in social behavior and reasoning.
Gregory and other researchers are investigating oxytocin to treat some of the symptoms of autism.
About one in 88 American children have an autism diagnosis, according to the Centers for Disease Control and Prevention.
Rather than one disease, autism is now regarded as a collection of conditions with similar traits but different causes, Rosanoff says. People on the autism spectrum are extremely diverse. Some are non-verbal and profoundly disabled; others have successful careers, particularly in science and technology, describing themselves as different, rather than disabled.
"Autism is so heterogeneous," Rosanoff says. "We're never going to get to the one cause."