This article was published in August of 2011 by the the Official Journal of the American Academy of Pediatrics. It's the largest study ever done on autism recurrence risk in younger siblings.
Why do I care? Because:
RESULTS: A total of 18.7% of the infants developed ASD. Infant gender and the presence of >1 older affected sibling were significant predictors of ASD outcome, and there was an almost threefold increase in risk for male subjects and an additional twofold increase in risk if there was >1 older affected sibling. The age of the infant at study enrollment, the gender and functioning level of the infant's older sibling, and other demographic factors did not predict ASD outcome.
We were told that because we have a daughter with autism, our chances of having a younger sibling with autism were significantly increased. However, this article tells us plain as day that this is simply not true.
Oh and here's another current article with the same findings.
You don't even have to read the article, the title speaks for itself:
Lack of evidence for increased genetic loading for autism among families of affected females.
I'm not saying we're out of the woods, I'm just saying... our odds of autism recurrence in our third child (if we had one) are the same as a family who had an older male sibling.
And the fact that we have Owen, who is developing perfectly, actually decreases our odds.
Triple boom boom boom.
Why did the doctor tell us differently?
Because some study done in Utah in the 1980's used a theory called the "multifactorial threshold model of transmission, in which risk is elevated for relatives of a proband (child with autism) in which the condition is less common."
This has reinforced that I need to do my own research instead of take what my doctors spoon feed me. I love doctors and I think they have the greatest intentions, but with the internet and nearly unlimited access to medical journals and peer reviewed articles, I think I'll be taking ownership of research significantly more than before.