The use of twin registers in the study of birth defects.
D000704:Analysis of Variance; D000013:Congenital Abnormalities / Q000235:genetics*; D004200:Diseases in Twins; D005260:Female; D005787:Gene Frequency; D006801:Humans; D008297:Male; D011247:Pregnancy; D012042:Registries; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic