Can mammalian mothers influence the sex of their offspring peri-conceptually?

Abstract

Although controversial, growing evidence from evolutionary biology suggests that the mammalian mother may have a role in influencing the sex of her offspring. However, there is competing information on the molecular mechanisms by which such influence could be manifested. The new initiatives are based on hypotheses from evolutionary biology: the 'good condition' hypothesis, which suggests that post conception, higher levels of maternal glucose may differentially promote the development of male embryos; and the 'maternal dominance' hypothesis, which proposes that before conception, higher follicular testosterone may influence the development of the ovum so that it emerges already adapted to receive an X-or a Y-chromosome-bearing spermatozoon. Now, it seems these hypothesised mechanisms could be operating in synchrony, each complementing and reinforcing the other. On the other hand, there are continuing problems in identifying a precise sequence of mechanisms as evidenced from research in sperm-sorting. Research on high-fat diets and the sex ratio in polytocous species may indicate important differences in proximate mechanisms for sex allocation between polytocous and monotocous mammals.

A trade-off between having many sons and shorter maternal post-reproductive survival in pre-industrial Finland

“…As originally proposed [15], the negative influence of producing many sons might be related to female hormone profiles. In mammals, accumulating evidence now suggests that high concentrations of circulating maternal testosterone skews offspring sex ratio towards males [23,24]. High levels of testosterone are also known to impair maternal immune function [25] and may thus explain the potential negative association between the number of sons born and post-reproductive survival in women.…”

Hypotheses on the stability and variation of human sex ratios at birth

“…This hypothesis was later supplemented by others proposing that high testosterone and/or oestrogen levels in either parent were associated with the births of subsequent sons (James, 1986). The evidence later adduced on this role of testosterone is strong and has been summarised in regard to men (James, 2006b); and to women and other female mammals by Grant et al (Grant, 2007;Grant and Chamley, 2010;Grant and Irwin, 2005;Grant et al, 2008).…”

Sex of offspring influences metabolism during early transition period in dairy cows

“…While many studies have focused on how mammalian females could influence the sex of the offspring both before and after conception (Hardy, 1997;Grant et al, 2008;Grant and Chamley, 2010), there is little understanding of how offspring sex can affect metabolism in dairy cows during the transition period. Fetal hormones may provide a means for understanding the influence of offspring sex on maternal metabolism during the early transition period, especially since they can readily diffuse into maternal circulation.…”