A quarterly publication of the Autism Research Institute

The Autism Research Review International is quarterly publication of the Autism Research Institute

Winter, 2017 | Number 1, Volume 31

Prenatal exposure to meconium may up autism risk slightly

Babies who have a bowel movement before birth have an increased risk of autism, researchers report, but the risk is very small. 

K. M. Miller and colleagues analyzed the hospital records of nearly 10 million children born in California between 1991 and 2008, comparing children exposed before birth to meconium (the first bowel movement) to those who had their first bowel movement after birth. In addition, they identified children who experienced meconium aspiration syndrome (MAS), in which meconium enters the lungs and can cause breathing problems. 

The researchers found that children with meconium-stained amniotic fluid caused by a prenatal bowel movement had an 18 percent increase in autism risk. Surprisingly, children with MAS had a smaller risk that failed to achieve significance. Study coauthor Cheryl Walker speculates that the interventions that children with MAS typically receive, such as oxygen and intravenous fluids, may reduce their risk for brain damage.


“Meconium exposure and autism risk,” K. M. Miller, G. Xing, and C. K. Walker, Journal of Perinatology, Vol. 37, February 2017, 203-7. Address: CK Walker, Mind Institute, Department of Obstetrics & Gynecology, 4869 Y Street, Suite 2500, Sacramento, CA 95817, [email protected].