Families who have an autistic child are less likely to have additional kids, a new study finds. The study, led by a UC San Francisco researcher, indicates that such families are roughly one third less likely to have more kids than families without an affected child.

According to the study findings, which appear in the June 18 issue of JAMA Psychiatry, this is a reproductive decision.

The findings come from the largest study of its kind regarding continuing to have children after a child has been diagnosed with autism.

Neil Risch, PhD, UCSF professor of epidemiology and biostatistics and director of the UCSF Institute for Human Genetics, said in a statement, “While it has been postulated that parents who have a child with ASD may be reluctant to have more children, this is first time that anyone has analyzed the question with hard numbers.”

Prior research has not accounted for the possibility of parents with an affected child to stop reproducing, resulting in previous estimates of having a child with autism potentially making the risk seem lower than it really is.

According to Autism Speaks, autism is a general term for a cluster of complex brain development disorders. The disorders are characterized by varying degrees of trouble with social interaction, verbal and nonverbal communication, and repetitive behaviors.