Sex-differential placentation immunological interactions between male conceptus and gravida during normal pregnancy.

7,773 placentae of newborns were analyzed in order to test a hypothesis of specific immunological concepto-maternal interactions due to maleness and occurring during normal pregnancy. An association between placental weight of newborn male and the sex of conceptuses of previous pregnancies was found which supports the hypothesis. No such an association was found for female newborn. The confirmation of these results could open new avenues in the study of sex-differential survival of the conceptus throughout gestation.