Table 3.
Association between twinning and selected birth defects stratified by estimated zygosity, National Birth Defects Prevention Study, 1997–2007
| Type of birth defect | Singleton (n) | Unlike-sex twin pairs (n) | Unlike-sex twin crude OR (95% CI)* | Estimated dizygotic twin crude OR (95% uncertainty interval) | Like-sex twin pairs (n) | Like-sex twin crude OR (95% CI) | Estimated monozygotic twin crude OR (95% uncertainty interval) |
|---|---|---|---|---|---|---|---|
| Controls | 7072† | 62 | Ref. | Ref. | 109 | Ref. | Ref. |
| Central nervous system | |||||||
| Anencephaly | 352 | 4 | NC | 1.5 (1.0 to 2.1) | 12 | 2.2 (1.2 to 4.0) | 2.9 (1.3 to 4.6) |
| Spina bifida | 747 | 4 | NC | 0.8 (0.5 to 1.1) | 15 | 1.3 (0.7 to 2.2) | 1.7 (0.9 to 2.6) |
| Hydrocephalus | 307 | 2 | NC | 1.8 (1.1 to 2.7) | 17 | 3.5 (2.1 to 6.0) | 4.6 (2.3 to 7.1) |
| Cataracts and other lens defects | 202 | 4 | NC | 1.9 (1.2 to 2.6) | 5 | 1.7 (0.7 to 4.3) | 2.2 (0.6 to 4.2) |
| Anotia/microtia | 383 | 9 | 2.5 (1.3 to 5.0) | 1.7 (1.3 to 2.1) | 5 | 0.8 (0.3 to 1.9) | 1.1 (0.3 to 2.0) |
| Cardiovascular | |||||||
| Dextro-transposition of great arteries | 502 | 8 | 1.8 (0.9 to 3.8) | 1.2 (0.9 to 1.5) | 6 | 0.8 (0.3 to 1.8) | 1.0 (0.3 to 1.8) |
| Tetralogy of Fallot | 737 | 9 | 1.4 (0.7 to 2.8) | 1.8 (1.4 to 2.3) | 32 | 2.8 (1.9 to 4.2) | 3.6 (2.3 to 5.1) |
| Perimembranous ventricular septal defects | 1320 | 27 | 2.5 (1.6 to 3.9) | 2.5 (2.1 to 2.9) | 58 | 3.0 (2.2 to 4.2) | 3.9 (2.8 to 5.4) |
| Secundum atrial septal defect | 1408 | 22 | 1.8 (1.1 to 2.9) | 2.2 (1.8 to 2.5) | 75 | 3.4 (2.5 to 4.6) | 4.2 (3.2 to 5.6) |
| Pulmonary valve stenosis | 822 | 13 | 1.7 (0.9 to 3.1) | 2.2 (1.8 to 2.7) | 45 | 3.5 (2.4 to 4.9) | 4.5 (3.1 to 6.2) |
| Coarctation of the aorta | 621 | 16 | 2.9 (1.7 to 5.1) | 2.6 (2.1 to 3.1) | 28 | 2.9 (1.9 to 4.4) | 3.8 (2.5 to 5.6) |
| Aortic stenosis | 254 | 6 | 2.7 (1.2 to 6.3) | 2.2 (1.6 to 2.8) | 8 | 2.0 (1.0 to 4.2) | 2.6 (0.8 to 4.4) |
| Hypoplastic left heart syndrome | 362 | 7 | 2.2 (1.0 to 4.8) | 1.7 (1.3 to 2.2) | 8 | 1.4 (0.7 to 2.9) | 1.9 (0.7 to 3.1) |
| Orofacial | |||||||
| Cleft lip±cleft palate | 2020 | 28 | 1.7 (1.1 to 2.6) | 1.3 (1.1 to 1.6) | 36 | 1.2 (0.8 to 1.8) | 1.6 (1.0 to 2.3) |
| Cleft palate | 1087 | 11 | 1.2 (0.7 to 2.4) | 1.2 (0.9 to 1.5) | 23 | 1.5 (0.9 to 2.3) | 1.9 (1.2 to 2.7) |
| Gastrointestinal | |||||||
| Oesophageal atresia with/without | 444 | 7 | 1.9 (0.9 to 4.3) | 2.7 (2.0 to 3.5) | 27 | 4.2 (2.8 to 6.5) | 5.5 (3.4 to 8.0) |
| tracheoesophageal fistula | |||||||
| Small intestinal atresia | 301 | 5 | 2.0 (0.8 to 5.0) | 1.8 (1.2 to 2.4) | 9 | 2.1 (1.0 to 4.1) | 2.7 (1.0 to 4.5) |
| Anorectal atresia | 681 | 8 | 1.4 (0.7 to 2.9) | 1.7 (1.3 to 2.2) | 26 | 2.6 (1.7 to 4.0) | 3.0 (1.9 to 4.2) |
| Hypospadias‡ | 1480 | 27 | 2.2 (1.3 to 3.6) | 2.1 (1.7 to 2.5) | 55 | 2.6 (1.8 to 3.5) | 3.3 (2.2 to 4.7) |
| Musculoskeletal | |||||||
| Longitudinal limb deficiency | 304 | 6 | 2.5 (1.1 to 5.8) | 2.3 (1.6 to 3.0) | 11 | 2.6 (1.4 to 4.9) | 3.4 (1.6 to 5.5) |
| Transverse limb deficiency | 465 | 6 | 1.6 (0.7 to 3.8) | 1.6 (1.1 to 2.0) | 12 | 1.8 (1.0 to 3.4) | 2.4 (1.2 to 3.8) |
| Craniosynostosis | 962 | 14 | 2.0 (1.1 to 3.6) | 1.4 (1.2 to 1.7) | 14 | 1.1 (0.7 to 2.0) | 1.5 (0.7 to 2.2) |
| Diaphragmatic hernia | 566 | 9 | 2.0 (1.0 to 4.0) | 1.4 (1.1 to 1.7) | 8 | 1.0 (0.5 to 2.1) | 1.3 (0.5 to 2.2) |
| Omphalocele | 290 | 2 | NC | 2.2 (0.9 to 4.2) | 12 | 2.9 (1.6 to 5.3) | 3.4 (1.8 to 5.7) |
| Gastroschisis | 898 | 5 | 0.7 (0.3 to 1.8) | 0.7 (0.5 to 1.1) | 11 | 0.9 (0.5 to 1.7) | 1.4 (0.9 to 2.0) |
*
Bold values indicate p<0.05.
†
Cases and controls from the Utah study site were not included in these analyses.
‡
Controls limited to male infants.
NC, not calculated because ≤4 twin pregnancies.