The sex ratios of families with a neurodevelopmentally disordered child.

It has been conjectured that mothers who give birth to neurodevelopmentally disordered (ND) children may have hormonal or immunological characteristics that bias them toward giving birth to male children. We examined this hypothesis in an epidemiological sample of 2,080 ND children drawn for the National Collaborative Perinatal Project (NCPP) who had one of nine kinds of NDs. No assumptions were made regarding the sex ratio of non-ND children since this could be computed from NCPP data for 11,213 families. The sex ratio of families with ND children was not significantly biased toward boys as compared to the sex ratio of families with non-ND children, provided that the index ND child was excluded from the analysis.