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• LINDSAY GELLMAN
• CONNECT

Pregnant women who have procedures to induce or encourage labor might have an increased risk of bearing a child with autism, according to a new study.

Researchers at Duke University and the University of Michigan who conducted the study, published Monday in the journal JAMA Pediatrics, said it doesn't prove that induced and/or augmented labor causes autism. Instead, it suggests that a link exists between the circumstances surrounding these delivery procedures and autism diagnosis in childhood.

The researchers don't suggest any change in medical practices based on their findings.

Both induction and augmentation have seen a significant rise in popularity, according to the most recent numbers available from the National Vital Statistics Reports. In 2010, 23.4% of deliveries were induced, an increase from 9.5% in the early 1990s. Data from 2002, the most recent available, show 17.3% of deliveries were augmented that year; only 10.9% were in 1989.

Induction refers to the stimulation of uterine contractions before a woman goes into labor. Augmentation is increasing the strength, duration or frequency of uterine contractions once she has gone into labor.

Women should speak to a health-care professional about the risks and benefits associated with induction and augmentation, says Simon G. Gregory, lead author of the study and associate professor of medicine and medical genetics at Duke.

A woman might need her labor induced or augmented because her health or the health of the child is at risk during delivery, says Chad A. Grotegut, an obstetrician and gynecologist at Duke University Medical Center and a co-author of the study. For example, a mother with hypertension or diabetes or who is well past her due date, or a fetus with growth abnormalities, might require induction.

Some women elect to be induced even if the procedure isn't necessary, typically with the aim of delivering the baby sooner, Dr. Grotegut says.

The researchers culled records of all live births in North Carolina between 1990 and 1998. They matched hospital data from 625,042 children to corresponding school records, which indicated whether the child had a documented "exceptionality designation for autism"—meaning the child had been diagnosed with the disorder by a psychologist.

One in 88 children in the U.S. is diagnosed with an autism-spectrum disorder, which is characterized by "core deficits in social interaction, language development, and patterns of repetitive behaviors and/or restricted interests," the study said. Males are about four times as likely to be diagnosed with autism as females.

The North Carolina data showed that the percentage of mothers who had induced and/or augmented labor was higher for those whose children were later diagnosed with autism than for mothers whose offspring didn't develop the disorder. Mothers whose labor was both induced and augmented had a 23% greater risk of bearing a child with autism than mothers who had neither procedure.

Breaking the data down by the child's sex, the researchers found that male children born to mothers who were both induced and augmented were at a 35% greater risk of being diagnosed with autism compared with males whose mothers had neither procedure. Males whose mothers were augmented had a 15% greater risk of being diagnosed with autism than males whose mothers had neither procedure. Females whose mothers were augmented had an 18% greater risk compared with female controls.

The researchers said the study data was controlled to account for factors such as maternal age and certain health conditions, including diabetes. They said they lacked data on where on the autism spectrum the diagnosed children fell, paternal age and medications the mother took during pregnancy.

More research is needed to establish whether the induction and/or augmentation procedures themselves increase the risk for autism, or whether the underlying conditions that necessitate the procedures—among other genetic and environmental factors—increase the risk, say experts from Autism Speaks, an autism-advocacy organization.