Could medicine commonly given to pregnant women to speed childbirth have an effect on which children develop autism? That provocative theory has been kicking around in some medical circles for more than a decade. But even today, no one knows the answer.
A new study, though, suggests that it's a question worth answering. Kids born to women who received drugs to help start or accelerate labor, researchers found, face an elevated risk of later being diagnosed with autism or a related cognitive disorder. The increase was small, but with millions of children born each year nationwide, it could be significant.
The link, reported Monday in the journal JAMA Pediatrics by researchers at Duke University, doesn't necessarily mean that so-called medically assisted labor contributes directly to higher autism risk. There are several other possible – and perhaps likelier – explanations. Universally, experts consulted by U.S. News urged doctors and patients to not change their behavior until the link has been more thoroughly investigated.
"These findings are important, but ... not a reason for concern on the part of expectant mothers," said Katy Backes Kozhimannil, a professor of health policy at the University of Minnesota School of Public Health. Both induction (the term for medical treatment to start labor) and augmentation (treatment to accelerate it) can often be crucial to ensuring the health of mother and child. Doctors decide it's best to induce women in an estimated 30 percent of all pregnancies, Kozhimannil said. Approximately half of labors involve augmentation.
"Women should not conclude that if they need induction or augmentation their child will have or be at high risk for autism. Nor should they seek to avoid induction [or] augmentation," said Jeffrey L. Ecker, an obstetrician at Massachusetts General Hospital. "The latter reaction would ... almost certainly [increase rates of] cesarean delivery, an intervention that we know has important [negative] effects on both maternal and neonatal health."
[Read: What You Need to Know About Autism.]
The Duke researchers examined some 625,000 births occurring in the 1990s in North Carolina and compared them to state educational records for subsequent years. They studied which children were diagnosed with an autism spectrum disorder and what the circumstances surrounding their births had been. After adjusting their data to account for factors such as gender and known maternal health conditions, the researchers estimated that approximately 2 autism cases out of every 1,000 diagnoses could be linked to whether the child's mom had medically assisted labor. Nationwide, about 1 child in 88 is diagnosed with autism spectrum disorder, according to the Centers for Disease Control and Prevention.
One of several possible explanations for the link is that pitocin, a medication widely used to trigger labor contractions, could have previously unrecognized effects on the newborn brain, according to Simon G. Gregory, the Duke geneticist who led the study. Pitocin is a manmade form of the naturally occurring hormone oxytocin, which plays an important role in cognitive function and social behavior; oxytocin is sometimes dubbed the "love hormone." In an earlier study, Gregory and his colleagues compared people with and without autism and found biological differences in cellular machinery that responds to oxytocin.
Gregory emphasized that further research is necessary to tease out what role, if any, pitocin exposure might play in cognitive development. As an important medicine, it has been used widely for many years and is generally thought to be harmless.
[Read: An All-Out Assault on Autism.]
Several researchers not involved in the study cautioned that factors other than pitocin are probably more likely to account for the study's findings.
For example, autism risk could have been elevated by certain complications that cause doctors to administer pitocin. In that scenario, the complication – not induction or augmentation itself – could be the factor contributing to higher risk of a cognitive disorder. When a woman's water breaks earlier than it should, for instance, doctors often decide to induce to minimize the risk of a dangerous infection. But even with induction, mild infections are not uncommon in such situations, and they could potentially trigger brain changes that leave the baby more susceptible to autism, said Jennifer Bailit, an obstetrician at Metrohealth Medical Center in Cleveland.
Alternatively, the seemingly higher rate of autism in children born by induction could be a statistical mirage. Bailit noted that mothers in the study who'd graduated college were one-third more likely to have children diagnosed with autism than were mothers who'd completed high school but not attended college. That's probably not because either group actually experiences higher rates of autism, but rather because kids who develop autism are more likely to receive a doctor's diagnosis if their parents are well educated. Interestingly, Bailit noted, well-educated women are also more likely to undergo induction. That alone, she suggested, could account for the link found by the Duke team.
Other researchers emphasized that inductions, while often medically necessary, should be avoided whenever they're unnecessary. For many years, so-called elective inductions were common in some hospitals. Sometimes doctors induced women before the fetus had fully matured, leading to avoidable health problems in the newborn. Medical experts and hospital leaders have cracked down on that dangerous practice in recent years, and now strongly discourage doctors and patients from electing to induce unless there's a strong medical reason to do so or the fetus is at least 39 weeks old.
Among women whose pregnancies haven't yet reached 39 weeks, said obstetrician/gynecologist Susan C. Mann of Beth Israel Deaconness Medical Center in Boston, "most hospitals these days since about 2011 have a hard stop on medically [unnecessary] inductions."
[Read: Signs Your Child Could Have Autism.]