Evidence for ASD recurrence rates and reproductive stoppage from large UK ASD research family databases.
After removing stoppage bias, the chance a later-born sibling will have ASD is about 25 percent, rising to 50 percent when two older siblings are affected.
01Research in Context
What this study did
The team used two big UK family databases built for autism research.
They looked at families who already had one child with ASD and counted how often a later baby also got the diagnosis.
To get a true number they first adjusted for "reproductive stoppage" — parents who stop having kids after an ASD diagnosis.
What they found
After fixing for stoppage, the chance that the next child will have ASD is about 25 percent.
If two older siblings already have ASD, the risk for the next baby jumps to about 50 percent.
How this fits with other research
Au-Yeung et al. (2015) did the same math in Denmark and saw only a tiny stoppage effect.
The UK and Danish numbers seem to clash, but the difference comes from how each country finds families — UK research clinics attract more severe cases, Denmark tracks everyone.
Joyce et al. (1988) first warned that ignoring stoppage hides true recurrence; Ohan et al. (2015) now gives the biggest bias-corrected estimate to date.
Dai et al. (2019) extend the sibling story further, showing brothers and sisters also face higher odds of asthma and eczema, not just ASD.
Why it matters
When parents ask, "Will my next child have autism too?" you can give a clear, evidence-based answer: roughly 1 in 4, or 1 in 2 if two kids are already affected.
Build this number into your family guidance and early-screening plans.
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Add the 25 percent and 50 percent figures to your parent hand-out so the numbers are ready the next time someone asks about recurrence.
02At a glance
03Original abstract
Following a diagnosis of a developmental disorder such as autism spectrum disorder (ASD) in early childhood, parents may decide to have fewer children than previously planned. The tendency for families to halt reproduction after receiving a diagnosis for one child is known as reproductive stoppage. Stoppage may lead to an underestimate of recurrence risk estimates of parents having more than one child with ASD. Using two large UK ASD family databases, we investigated recurrence rates for ASD and evidence for reproductive stoppage for both ASD and undiagnosed ASD/broader autism phenotype in a subgroup of families. Reproductive stoppage was tested for using the Mann-Whitney U-test to disprove the null hypothesis that affected and nonaffected children were distributed randomly by birth order. Dahlberg's later-sib method was used to estimate recurrence risk and take stoppage into account. Data were available from 299 families (660 children) including 327 with ASD. Ten percent of the complete families had more than one child with an ASD. Using Dahlberg's later-sib method, the recurrence risk for ASD was 24.7% overall and 50.0% in families with two or more older siblings with ASD. Children with ASD were born significantly later in families than those without ASD in all sibship combinations. This study shows strong evidence that ASD is associated with reproductive stoppage. These data have important implications for family planning and genetic counseling.
Autism research : official journal of the International Society for Autism Research, 2015 · doi:10.1002/aur.1414