A mother's immune system may have a defensive response to substances produced by male fetuses.This is most likely to contribute to
A) erotic plasticity.
B) female orgasmic disorder.
C) sexually transmitted infections.
D) the fraternal birth-order effect.

Question

A mother's immune system may have a defensive response to substances produced by male fetuses.This is most likely to contribute to
A) erotic plasticity.
B) female orgasmic disorder.
C) sexually transmitted infections.
D) the fraternal birth-order effect.

Quizplus · Accepted Answer

The fraternal birth-order effect refers to the phenomenon where the likelihood of a male fetus being gay increases with each older brother he has. This effect is thought to be related to a mother's immune system developing a defensive response to substances produced by male fetuses, which may then affect the brain development of subsequent male fetuses.

A Mother's Immune System May Have a Defensive Response to Substances