Abstract
Autism is a neurodevelopment disorder with a strikingly higher prevalence in boys than girls. There are many theories regarding this gender bias, and prenatal exposure to high levels of fetal testosterone (FT) may be a predisposing factor. The second to fourth digit ratio (2D:4D) is the only indirect measure that reflects this association postnatally. Thus, this study measured the lengths of the index finger (2D) and the ring finger (4D) and calculated the 2D:4D ratio. Subsequently, this ratio was used to indirectly determine the potential prenatal exposure to high levels of FT in autistic children.
This case–control study was conducted with 60 male children with 31 individuals having classic-onset autism and 29 individuals serving as age-matched, healthy controls. The lengths of both the index (2D) and the ring (4D) fingers of the right hand of both autism and control groups were obtained using a scanner and the 2D:4D ratio was calculated.
The 2D:4D ratio in the current study was significantly lower in boys with autism compared to the controls (p≤0.001).
This study demonstrates a significantly lower 2D:4D ratio in Saudi boys with autism, which indirectly suggests that these boys were exposed to high levels of prenatal FT. Accordingly, prenatal exposure to high levels of FT is a risk factor for the development of autism, and the postnatal measurement of the 2D:4D ratio could be a potential screening tool.
•Prenatal exposure to high levels of fetal testosterone (FT) is a proposed theory for autism.•The 2D:4D reflects this exposure prenatally.•It is a case–control study conducted with 60 male children.•31 individuals have classic-onset autism and 29 individuals serve as age-matched, healthy controls.•The results showed that the 2D:4D was significantly lower in boys with autism compared to the controls (p≤0.001).