So maybe this explains the fact that we wound up with four boys… A recent study out of the Czech Republic concluded that women infected with Toxoplasma gondii are more likely to give birth to boys than are women who are toxoplamosis-free. In most populations, 51% of babies born are males, but in women infected with Toxoplasmosis that rate climbs to 61%. Moreover, the higher the antibody level in the mother, the more likely she was to have a boy.
People generally contract Toxoplasmosis by eating undercooked meat, or by being exposed to cat feces. Babies of women who contract the disease during pregnancy are at risk of birth defects including mental retardation, deafness, and blindness. Children of women infected six or more months prior to pregnancy are not thought to face these same risks, although the authors of the study did suggest that Toxoplasmosis might affect a woman’s immune system in a way that makes male embryos more likely to survive than female embryos. This is the first study ever to suggest a link between a parasitic infection and the sex of a baby.