A mother's immune system may have a defensive response to substances produced by male fetuses.This is most likely to contribute to

Question

Quizplus · Accepted Answer

The older-brother effect refers to the phenomenon where having older brothers increases the likelihood of a male fetus being homosexual. One theory behind this effect is that the mother's immune system develops a defensive response to substances produced by male fetuses, which may affect the sexual orientation of subsequent male fetuses. This suggests that the mother's immune system plays a role in sexual orientation, but not in sexual dysfunction, refractory periods, or sexually transmitted infections.

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