Increased Prevalence of Congenital Heart Defects in Monozygotic and Dizygotic Twins
Background—Smaller studies and many case series reports indicate that congenital heart defects (CHD) may be more common in monochorionic twins than in dichorionic twins and singletons.
Methods and Results—We investigated CHD occurrence in all twins and 5% of all singletons born in Denmark in the period 1977-2001 and followed through 2006, by linking the Danish Twin Registry and Statistics Denmark registers including the National Birth Register and the Danish National Patient Register. Among 41,525 twin individuals, a total of 584 twins (1.4%) had a CHD registered in the Danish National Patient Register, while the corresponding numbers for singletons were 648/74,473 (0.87%) (p<0.001), i.e. a 63% (95% CI: 45-82%) increased risk for CHD for twins. Patent ductus arteriosus and coarctation of aorta occurred more than three times as often in twins as in singletons: 3.9 (95% CI: 2.6-5.8) and 3.1(95% CI:1.5-6.4), respectively. The increased occurrence in twins was also found in sensitivity analyses including only inpatients or only surgically treated cases regardless of whether preterm patent ductus arteriosus was included or not. We were not able to demonstrate a higher risk for CHD among monozygotic twins compared to dizygotic twins and the CHD occurrence was also increased in dizygotic twins, which are all dichorionic.
Conclusions—CHD is more common in twins than in singletons, and the increased occurrence is not restricted to monochorionic twins. Intrauterine surveillance and a postnatal comprehensive cardiac assessment for both twins may be considered regardless of chorionicity and zygosity.
- Received March 6, 2013.
- Revision received June 20, 2013.
- Accepted July 12, 2013.