title: Interactions between opposite-sex dizygotic fetuses and the assumptions of Weinberg difference method epidemiology.
abstract: The Weinberg difference method in twin epidemiology may be subject to a major error related to a fundamental assumption that seems not to have been previously questioned. Results presented here indicate that the mortality of like-sex dizygotics (DZs) resembles that of monozygotics (MZs) much more than that of unlike-sex DZs, who are not representative of any other group. Unlike-sex twins enjoy a relative protection from fetal and neonatal mortality and probably from at least one effect of the transient perinatal hypoxia common for second twins. Unlike-sex twins develop, and maintain into adulthood, an intermediate gender phenotype with respect to integration of craniofacial growth.
mesh_terms: D001722:Birth Order; D002823:Chorion; D000013:Congenital Abnormalities / Q000235:genetics; D004200:Diseases in Twins; D005260:Female; D005313:Fetal Death / Q000235:genetics; D007839:Functional Laterality; D005826:Genetics, Medical; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D008957:Models, Genetic; D009026:Mortality; D011247:Pregnancy; D012737:Sex Factors; D012744:Sex Ratio; D014427:Twins; D014429:Twins, Dizygotic