Can mothers-to-be control sex of fetus?

Mothers can adjust the sex of their unborn children to match the quality of their living conditions, a new study has revealed. Genetics are a factor, but it's believed that mothers exert far more control than dads do. Stress hormones circulating in mother may help to drive the process. The study finds that mothers exert far more control than fathers do over whether or not the couple has a son or daughter. The goal is to improve the child's survival.

"It seems likely that when there are large and predictable costs associated with producing and/or rearing either sons or daughters in a given environment, females should bias offspring sex ratios to produce the sex that will perform best in the given environment," co-author Sarah Pryke told Discovery News.

"Altering offspring sex ratios in response to the quality of the local environment is likely to be highly advantageous to any species, as it should allow mothers to best match the phenotype of their offspring to the prevailing condition, and thus maximize their own fitness," she said.

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