Evidence that mammalian sex ratios at birth are partially controlled by parental hormone levels around the time of conception

Abstract

An attempt is made to summarize the evidence that the offspring sex ratios (proportions male at birth) of mammals (including man) are causally related to the hormone levels of both parents around the time of conception. Almost all of the cited studies were reported by non-endocrinologists. This being so, it would seem desirable to have comments of endocrinologists on this topic.

The Influence of Migration on Secular Trends in Sex Ratios at Birth in Cuba in the Past Fifty Years

“…This ratio is conventionally expressed as the ratio of male live births divided by total live births (M/F). The reason for this discrepancy is uncertain but several factors have been proposed (2).…”

Maternal height and the sex ratio

“…Other theories such as GRANT (1994) andJAMES (1996) generate similar predictions and have linked testosterone levels to human sex ratios. For instance, Grant's Maternal Dominance hypothesis suggests that relatively more dominant mothers have a higher likelihood of male offspring.…”

The Most Widely Publicized Gender Problem in Human Genetics

“…Sex ratios can be influenced by numerous factors (Edwards 1966;Jacobsen et al 1999;James 1976James , 1985James , 1987aJames , 1987bJames , 1995James , 1996James , 2001James , 2008McWhirter 1956;Pickles et al 1982). Edmond Malinvaud (1955) studied almost 4 million births in France for [1946][1947][1948][1949][1950] and concluded that the probability estimate p (mea sured as a percentage) of a pregnancy producing a boy is fairly well fitted by the linear relationship p = 51.45 + 0.3n − 0.5m, where n is the number of preexisting boys and m is the number of preexisting girls in the sibship.…”