Table 4. Parental smoking status and risk of birth anomalies in the California Twin Program (Birth cohort 1957–1982, N = 20,803 pairs).
| Affected (Concordant+Discordant) vs Unaffected |
Neither Smoking N (%) |
Only father smoking N (%) |
Only mother smoking N (%) |
Both smoking N (%) |
Father only vs Neither | Mother only vs Neither | Both vs Neither | P-value for quadratic trend | ||||
| ORAdj.* | 95% CI | ORAdj.* | 95% CI | ORAdj.* | 95% CI | |||||||
| Clubfoot | Affected (C+D) pairs | 23 (0.45) | 10 (0.30) | 11 (0.60) | 39 (0.76) | 0.63 | 0.30–1.34 | 1.27 | 0.61–2.61 | 1.53 | 0.90–2.60 | 0.029 |
| Unaffected pairs | 5,086 (99.55) | 3,303 (99.70) | 1,837 (99.40) | 5,123 (99.24) | 1 (ref) | 1 (ref) | 1 (ref) | |||||
| Oral cleft | Affected (C+D) pairs | 13 (0.25) | 6 (0.18) | 7 (0.38) | 10 (0.19) | 0.67 | 0.25–1.80 | 1.47 | 0.58–3.72 | 0.72 | 0.31–1.67 | 0.517 |
| Unaffected pairs | 5,096 (99.75) | 3,307 (99.82) | 1,841 (99.62) | 5,152 (99.81) | 1 (ref) | 1 (ref) | 1 (ref) | |||||
| Deafness | Affected (C+D) pairs | 50 (0.98) | 39 (1.18) | 13 (0.70) | 60 (1.16) | 1.13 | 0.73–1.73 | 0.69 | 0.37–1.27 | 1.10 | 0.75–1.62 | 0.291 |
| Unaffected pairs | 5,059 (99.02) | 3,274 (98.82) | 1,835 (99.30) | 5,102 (98.84) | 1 (ref) | 1 (ref) | 1 (ref) | |||||
| Cerebral palsy | Affected (C+D) pairs | 36 (0.70) | 19 (0.57) | 10 (0.54) | 37 (0.72) | 0.92 | 0.52–1.62 | 0.83 | 0.41–1.68 | 1.16 | 0.72–1.85 | 0.923 |
| Unaffected pairs | 5,073 (99.30) | 3,294 (99.43) | 1,838 (99.46) | 5,125 (99.28) | 1 (ref) | 1 (ref) | 1 (ref) | |||||
| Muscular dystrophy | Affected (C+D) pairs | 6 (0.12) | 1 (0.03) | 1 (0.05) | 5 (0.10) | 0.23 | 0.03–1.90 | 0.42 | 0.05–3.54 | 0.70 | 0.21–2.36 | 0.864 |
| Unaffected pairs | 5,103 (99.88) | 3,312 (99.97) | 1,847 (99.95) | 5,157 (99.90) | 1 (ref) | 1 (ref) | 1 (ref) | |||||
| Spina bifida | Affected (C+D) pairs | 7 (0.14) | 4 (0.12) | 4 (0.22) | 25 (0.48) | 0.88 | 0.25–3.03 | 1.60 | 0.47–5.51 | 3.48 | 1.48–8.18 | 0.026 |
| Unaffected pairs | 5,102 (99.86) | 3,309 (99.88) | 1,844 (99.78) | 5,137 (99.52) | 1 (ref) | 1 (ref) | 1 (ref) | |||||
| Strabismus | Affected (C+D) pairs | 130 (2.54) | 76 (2.29) | 54 (2.92) | 202 (3.91) | 0.91 | 0.68–1.22 | 1.19 | 0.86–1.65 | 1.61 | 1.28–2.03 | 0.0005 |
| Unaffected pairs | 4,979 (97.46) | 3,237 (97.71) | 1,794 (97.08) | 4,960 (96.09) | 1 (ref) | 1 (ref) | 1 (ref) | |||||
| Congenital heart defects | Affected (C+D) pairs | 66 (1.29) | 51 (1.54) | 28 (1.52) | 82 (1.59) | 1.19 | 0.82–1.73 | 1.18 | 0.76–1.85 | 1.23 | 0.88–1.72 | 0.491 |
| Unaffected pairs | 5,043 (98.71) | 3,262 (98.46) | 1,820 (98.48) | 5,080 (98.41) | 1 (ref) | 1 (ref) | 1 (ref) | |||||
*Adjusted for zygosity, gender, maternal age, parental education and birth order.