1. Noipayak P. {{The ratio of 2nd and 4th digit length in autistic children}}.{ J Med Assoc Thai};2009 (Aug);92(8):1040-1045.

OBJECTIVE: To compare 2D:4D ratios of autistic to non-autistic children as a risk factor of autism. MATERIAL AND METHOD: A hospital based case-control study was conducted from March 2007 to July 2008. Demographic data and general risk factors of autism had been collected using questionnaires from case and age matched control subjects aged 18 months to 15 years. Length of 2nd and 4th digits was measured by an electronic digital caliper. RESULTS: The ratio of right hand 2D:4D of autistic children was 0.99 +/- 0.06 compared with 1.02 +/- 0.04 of non-autistic children (p = 0.01). On the other hand, 2D:4D ratio of left hand of autistic children was 0.99 +/- 0.07 while the ratio of non-autistic children was 1.01 +/- 0.03 (p = 0.04). The 2D:4D ratio of both hands between 0.96 and 1.01 were risk factors of autism with odds ratio between 3.22 and 5.35 (p < 0.05). CONCLUSION: The ratios of 2D:4D of both hands of autistic children were higher than non-autistic children. The ratios of 2D:4D between 0.96 and 1.01 of both hands associated with an increased risk of autism in children aged 18 months to 15 years.