Sex differential of survival during perinatal period: an immunologic phenomenon?
The sex-differential early neonatal mortality experienced by a population of 27,243 neonates has been analyzed in relation to sex-related reproductive antecedents of their mothers. An association between the risk of dying of a neonate and the sex of previous pregnancies of its mother has been found: the risk decreases with a previous pregnancy of the same sex as the neonate, and increases with one of the opposite sex. Repeated pregnancies of same sex increase the phenomenon. An immunologic hypothesis has been formulated from these results: sex-differential survival of conceptuses during the perinatal period would be due to sex-differential conceptomaternal immunologic interactions. An advantage in survival of the female fetus results from these interactions in primiparous mothers. However, immunologic behavior of the mother is altered by previous contact with fetal antigens. Consequently sex-differential survival varies with sex-related antecedents of the gravida. Previous sensitization of the gravida by male pregnancy provides an advantage in survival for a subsequent male conceptus, and previous sensitization by female pregnancy provides an advantage in survival for a subsequent female conceptus.
D001722:Birth Order; D002140:California; D005260:Female; D005313:Fetal Death / Q000276:immunology*; D005333:Fetus / Q000276:immunology; D006801:Humans; D007226:Infant Mortality; D007231:Infant, Newborn; D008297:Male; D008431:Maternal-Fetal Exchange; D011247:Pregnancy; D012737:Sex Factors