Influence of the mother's preceding pregnancies on fetal development and postnatal survival of the neonate, in normal pregnancy. An immunological phenomenon?

Objectives: The objective of this study is to test for an association between the sex of conceptuses of the mother's preceding pregnancies and fetal development and early neonatal survival in normal pregnancy.

Methods: A population of 27,243 neonates, including a subsample of 7,773 "newborn/mother/placenta units" were divided into cohorts according to the sex of the neonate and the sex and number of conceptuses of the mother's preceding pregnancies. The average birth weight, placenta weight and early neonatal mortality rate were measured for each cohort and compared.