Have A Child With Autism? You May Be Unlikely To Try for Another

It's sad.  But families with an autistic child are about one-third less likely to have another child, according to newswise.com.

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

The Web site notes that the 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,” said Risch, who is senior author on the paper. “These findings have important implications for genetic counseling of affected families.”

Overall, families whose first child had ASD were one-third less likely to have a second child than control families, the study found. Families in which a later-born child was the first to be affected by ASD were equally less likely to have more children, newswise notes. Researchers said that subsequent childbearing appeared to be normal until the time an affected child would typically start to show symptoms or be diagnosed, indicating that the stoppage was likely the result of a parental choice or circumstance, rather than a reproductive problem.

The scientists found that when reproductive stoppage was taken into account, the odds of having another child with ASD significantly increased.

"Ignoring stoppage, the so-called recurrence risk (likelihood of another affected child) is 8.7 percent for full siblings and 3.2 percent for half-siblings from the same mother. Taking stoppage into account, the recurrence risk becomes 10.1 percent for full siblings and 4.8 percent for maternal half-siblings," newswise reports.

According to Risch, the findings do more than simply change the picture of risk for having another autistic child. “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.”

Paradoxically, you would think that if people with ASD in their family have fewer children, or none at all, the risk would drop.  But that's not the case. 

"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.”

In the year 2000, autism was reported in an estimated one child out of 150 in the United States, according to the Centers for Disease Control and Prevention. In 2010, the most recent data available, that rate had more than doubled, to one in 68 children.

Is that because we're recognizing ASD more?  Possibly.  But scientists are also postulating that it could also be some environmental factor, too.

"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.” 


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