Offspring sex ratio: Coital rates and other potential causal mechanisms

Offspring sex ratio: Coital rates and other potential causal mechanisms. William H.James, VictorGrech. Early Human Development, Volume 116, January 2018, Pages 24-27. https://doi.org/10.1016/j.earlhumdev.2017.10.006

Highlights
•    Sex ratios at birth (SRB) are elevated by increased coital rates.
•    Maternal stress induces male foetal losses.
•    Periconceptual parental hormone concentrations may influence SRB.
•    Understanding SRB influences may help understand causes of diseases with unusual SRB.
•    E.g.: testicular cancer, hepatitis B, Toxoplasma gondii and, perhaps, prostatic cancer

Abstract: In recent years, scientists have begun to pay serious attention to the hypothesis that human parental coital rates around the time of conception causally influences the sexes of subsequent births. In this paper, the grounds of the argument are outlined. The point is important because, if the hypothesis were credible, it can potentially explain one of the best established (and otherwise unexplained) epidemiological features of sex ratio at birth – its rises during and just after World Wars 1 and 2 insofar as increased coital rates increase the ratio. Moreover, the greater the understanding of the variations of sex ratio at birth, the greater will be the understanding of the causes of those selected diseases associated with unusual sex ratios at birth (testicular cancer, hepatitis B, Toxoplasma gondii, and, perhaps, prostatic cancer).