Frequency of CHD subtypes and severity categories according to plurality and chorionicity
| CHD subtype | Twins (any chorionicity) N (% of 154) | Dichorionic twins N (% of 96) | Monochorionic twins N (% of 47) | Singletons N (% of 2984) |
|---|---|---|---|---|
| Severe CHD | 7 (4.6) | 4 (4.2) | 3 (6.4) | 132 (4.4) |
| Single ventricle | 2 (1.3) | 1 (1.0) | 1 (2.1) | 15 (0.5) |
| Hypoplastic left heart | 2 (1.3) | 1 (1.0) | 1 (2.1) | 76 (2.6) |
| Hypoplastic right heart | 3 (2.0) | 2 (2.1) | 1 (2.1) | 41 (1.4) |
| Moderate CHD | 31 (20.1) | 25 (26.0) | 5 (10.6) | 712 (23.9) |
| Pulmonary valve atresia | 5 (3.3) | 5 (5.2) | 0 | 32 (1.1) |
| Common arterial trunk | 0 | 0 | 0 | 20 (0.7) |
| Atrioventricular septal defect | 2 (1.3) | 1 (1) | 1 (2.1) | 70 (2.4) |
| Aortic valve atresia/stenosis | 4 (2.6) | 3 (3.1) | 1 (2.1) | 100 (3.4) |
| Transposition of the great vessels | 2 (1.3) | 1 (1.0) | 1 (2.1) | 145 (4.9) |
| Tetralogy of Fallot | 6 (3.9) | 5 (5.2) | 1 (2.1) | 117 (3.9) |
| Total anomalous pulmonary venous return | 2 (1.3) | 2 (2.1) | 0 | 34 (1.1) |
| Coarctation of aorta | 10 (6.5) | 8 (8.3) | 1 (2.1) | 132 (4.4) |
| Double outlet RV | 0 | 0 | 0 | 18 (0.6) |
| Interrupted aortic arch | 0 | 0 | 0 | 11 (0.4) |
| Mitral valve anomalies | 0 | 0 | 0 | 33 (1.1) |
| Mild CHD | 106 (68.8) | 63 (65.6) | 35 (74.4) | 1967 (69.9) |
| Ventricular septal defect | 69 (44.8) | 39 (40.6) | 25 (53.2) | 1392 (46.7) |
| Atrial septal defect | 18 (11.7) | 12 (12.5) | 4 (8.5) | 339 (11.4) |
| Pulmonary valve stenosis | 19 (12.3) | 12 (12.5) | 6 (12.8) | 236 (7.9) |
| Other CHD | 10 (6.5) | 4 (4.2) | 4 (8.5) | 173 (5.8) |
| Patent ductus arteriosus (≥37 weeks) | 4 (2.6) | 1 (1.0) | 2 (4.3) | 58 (1.9) |
| Total | 154 (100.0) | 96 (100.0) | 47 (100.0) | 2984 (100.0) |
CHD, congenital heart disease.