June 19, 2014
Parents With An Autistic Child Often Opt Out Of Future Conception
Brett Smith for redOrbit.com - Your Universe Online
When many parents discover they have a child with autism spectrum disorder (ASD), they often decide against having additional children, and this phenomenon – known as reproductive stoppage – has skewed statistics on the chances an additional child would also develop the developmental condition, according to a new report in JAMA Psychiatry.
The study team noted that previous ASD research has ignored reproductive stoppage, and as a result – prior estimates of the probability of having another child with ASD could have made the danger appear less than it actually is.
"This study is the first to provide convincing statistical evidence that reproductive stoppage exists and should be taken into account when calculating the risks for having a another child with ASD," Risch said. "These findings have important implications for genetic counseling of affected families."
For the study, researchers examined data from California state health records and identified nearly 20,000 families that included at least one child with ASD between 1990 and 2003. The researchers also considered data from over 36,000 control families, which did not include a child with the condition.
The study team saw families whose very first child was diagnosed with ASD had been one-third less likely to have another child than those in the control group. Families involving a later-born child who was the first to be impacted by ASD were equally less likely to have additional children. Scientists said that future childbearing seemed to be normal until the time an affected child would normally start to exhibit symptoms or be diagnosed, implying that reproductive stoppage was likely the consequence of parental choice or circumstance, as opposed to a reproductive problem.
When reproductive stoppage was considered, the team saw the chances of having a second child with ASD appreciably raised. Ignoring stoppage, the odds of a second affected child is 8.7 percent for full siblings and 3.2 percent for half-siblings from the same mother. Considering stoppage, the risk becomes 10.1 percent for full siblings and 4.8 percent for maternal half-siblings.
Risch noted that the findings reflect more than simply a reproductive phenomenon in society.
"Our work shows that not only do people with ASD have fewer children than others," he said, "but in families where a child has ASD, the fact that the parents choose to have fewer children means the genes that predispose to ASD are less likely to be passed on to future generations."
He added that this situation leads to a sort of paradox.
"ASD has an important genetic component, which should be diminishing over time due to this reduction in childbearing," Risch said. "Yet over the past several decades, the incidence of ASD has risen dramatically."
According to co-author Lisa Croen, an epidemiologist and director of the Autism Research Program at Kaiser Permanente Northern California, parents may decide against having another child due to financial concerns or worries about the demands of additional care.
"Unfortunately, we still don't know what causes autism, or which specific conditions make it more likely," Croen said. "We are hoping that further research will enable us to identify both effective treatment strategies and, ultimately, modifiable causes of the disorder, so parents won't have to curtail their families for fear of having another affected child."