title: Influence of the mother's preceding pregnancies on fetal development and postnatal survival of the neonate, in normal pregnancy. An immunological phenomenon?
abstract: OBJECTIVE
  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. The "dose effect" of preceding pregnancy was tested by linear and quadratic regression analysis, and by chi-square trend test for linearity of proportions.
  
  
  RESULTS
  The results have shown an association between these three variables and the preceding pregnancies of the mother. Fetal development and early survival of the neonate are positively associated with the mother's preceding pregnancies of same sex as the neonate, and negatively associated with the preceding pregnancies of opposite sex to the neonate. The strength of the phenomenon increases with parity, at least for the first three parities. The association is statistically significant.
  
  
  CONCLUSIONS
  The association between fetal development and neonatal survival and preceding pregnancies of the mother would be compatible with the action of male and female specific antigens capable of affecting selective implantation of blastocysts, which commands subsequent fetal development as well as early neonatal survival.
authors.affiliation: School of Population and Public Health, University of British Columbia, Vancouver, BC, Canada. mvernier@interchange.ubc.ca
authors.forename: Michel C
authors.initials: MC
authors.lastname: Vernier
authors.forename: C J G
authors.initials: CJ
authors.lastname: Mackenzie
authors.forename: Michael
authors.initials: M
authors.lastname: Schulzer
authors.forename: Pierre R
authors.initials: PR
authors.lastname: Vernier
mesh_terms: D001722:Birth Order; D001724:Birth Weight; D015331:Cohort Studies; D005260:Female; D005313:Fetal Death / Q000276:immunology*; D047109:Fetal Development / Q000276:immunology*; D020073:Gravidity / Q000276:immunology*; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D008431:Maternal-Fetal Exchange; D010298:Parity / Q000276:immunology*; D054238:Perinatal Mortality; D010920:Placenta; D011247:Pregnancy; D012044:Regression Analysis; D012737:Sex Factors