Risk of autism connected to maternal age

The odds of having a child with autism for mothers aged 30 years or older rose by 18% for every five-year increase in age, indicating a link between advanced maternal age and risk of autism, according to a recently published study.

Researchers from the UC Davis Department of Public Health Sciences in California collected data from electronic records for all births in California between Jan. 1, 1990, and Dec. 31, 1999, and matched them with children who would later receive a diagnosis of autism from the California Department of Developmental Services. About 4.9 million births, with 12,159 cases of autism, comprised the study sample.

A 40-year-old woman’s risk of having a child later diagnosed with autism was 50% greater than a woman between 25 and 29. Advanced paternal age was also associated with an elevated risk for autism even when the mother was younger. For example, children fathered by a man older than 40 years were twice as likely to develop autism as those children with fathers between the ages of 25 and 29, among births to mothers younger than age 25. That association dissipated, however, among mothers older than 30 years.

“This study challenges a current theory in autism epidemiology that identifies the father’s age as a key factor in increasing the risk of having a child with autism,” Janie F. Shelton, a doctoral student from UC Davis Department of Public Health Sciences and a study researcher said in a press release.

Evidence also indicated that the number of California women older than age 40 years that gave birth increased throughout the 1990s, according to the researchers. However, this trend only accounted for about a 4.6% increase in autism diagnoses in California and did not substantially contribute to rising rates of autism.

Shelton JF. Autism Res. 2010; 10.1002/aur.116