Intrauterine growth restriction in like-sex twins discordant for structural defects

Birth Defects Res A Clin Mol Teratol. 2006 Apr;76(4):246-8. doi: 10.1002/bdra.20247.


Background: An increased risk for intrauterine growth restriction in the affected member of like-sex twin pairs discordant for hypospadias has been reported. The purpose of this study was to document patterns of birth weight disparities in like-sex twins discordant for a variety of structural defects in order to determine if this is a general phenomenon seen in twins who are discordant for any malformation, is seen only in pairs discordant for certain specific malformations, or is unique to hypospadias.

Methods: Data were extracted from the Latin American Collaborative Study of Congenital Malformations (ECLAMC). Between 1967 and 1999, all like-sex twin pairs discordant for hypospadias or any other isolated defect that met the criteria of at least 5 discordant pairs for which birth weight was available on both twins were selected. All nonmalformed like-sex twin pairs in the ECLAMC data base collected over the same study years were selected as controls.

Results: A total of 216 discordant malformed like-sex twin pairs in 13 defect categories and 328 nonmalformed like-sex twin pairs met the criteria for inclusion. The proportion of affected infants who were > or =20% smaller than their co-twin was statistically significantly different from controls for hypospadias, heart defects, anencephaly, and esophageal atresia.

Conclusions: Intrauterine growth restriction seen in the affected member of like-sex twin pairs discordant for hypospadias is not unique, but occurs as well in at least 3 additional structural malformations.

Publication types

  • Twin Study

MeSH terms

  • Birth Weight
  • Case-Control Studies
  • Congenital Abnormalities / epidemiology
  • Female
  • Fetal Growth Retardation*
  • Growth Disorders / genetics
  • Humans
  • Infant, Newborn
  • Karyotyping
  • Latin America / epidemiology
  • Pregnancy
  • Sex Characteristics
  • Twins*