Published online by Cambridge University Press: 01 August 2014
Source of data is “Survey on Socio-Economic Aspects of Vital Events – Plural Births in 1975”, including 12,392 twin pairs, 124 triplet sets, 7 quadruplet sets and 1 quintuplet set. Feal deaths were 3,285 for twins, 141 for triplets, 17 for quadruplets, and 5 for quintuplets, among which the numbers of birth defects were 78, 3, 0, and 0, respectively. Concordant twin pairs with the same category of birth defect were 20 among 56 pairs (0.36). As for the remaining 36 pairs, 2 pairs had different category of birth defects, 27 pairs had liveborn cotwins, and 7 pairs were both fetal deaths among which a twin had birth defect. The second-born twins had birth defects more frequently than the first-born twins among fetal deaths (28 vs 6).