title: Excess of like sexed pairs of dizygotic twins.
mesh_terms: D001789:Blood Group Antigens; D005260:Female; D005826:Genetics, Medical; D005828:Genetics, Population; D006801:Humans; D008297:Male; D011247:Pregnancy; D012723:Sex; D014427:Twins
chemical_list: D001789:Blood Group Antigens