J Acta Genet Med Gemellol (Roma). 1986;35(3-4):167-78.
Congenital malformations in twins: a population study.
K?l? B.
Malformations in twins were studied with the use of a
Medical Birth Registry covering nearly all births in
Sweden, 1973-1981. A total of 15,427 infants marked
twins were identified and the malformation diagnoses
were analyzed, comparing rates with the overall rates in
the same data source. Problems in ascertainment and
interpretation are discussed. No excess of neural tube
defects was seen, but hydrocephaly was diagnosed more
often in twins than in singletons. This can be partly,
but not completely, explained by a higher rate of
low-weight infants among twins. An excess was noticed in
twins in the rates of cardiac defects, spine defects,
gut atresias--notably esophageal and anal atresia--and
severe kidney malformations. These are components of the
so-called VACTERL syndrome--the last component (limb
reductions) being more common in twins than in
singletons, though statistical significance was not
reached. A relation between monozygotic twinning and
this syndrome is tentatively suggested.
