Table 2.
Parent and child characteristics
| Characteristics | Total | Without congenital limb abnormalities | All congenital limb abnormalities | ||||
| n = 90163 | 100% | n = 89794 | 100% | n = 369 | 100% | ||
| Mother | |||||||
| Age | <25 | 9026 | 10.01% | 9000 | 10.02% | 26 | 7.05% |
| 25 to <30 | 24961 | 27.68% | 24868 | 27.69% | 93 | 25.20% | |
| 30 to <35 | 31966 | 35.45% | 31824 | 35.44% | 142 | 38.48% | |
| 35+ | 24204 | 26.84% | 24096 | 26.83% | 108 | 29.27% | |
| Missing data | 6 | 0.01% | 6 | 0.01% | 0 | 0.00% | |
| Prepregnancy BMI | <18.5 | 14460 | 16.04% | 14406 | 16.04% | 54 | 14.63% |
| 18.5–25 | 66090 | 73.30% | 65819 | 73.30% | 271 | 73.44% | |
| 25+ | 9558 | 10.60% | 9514 | 10.60% | 44 | 11.92% | |
| Missing data | 55 | 0.06% | 55 | 0.06% | 0 | 0.00% | |
| Parity | Nulliparous | 36981 | 41.02% | 36823 | 41.01% | 158 | 42.82% |
| Multiparous | 53136 | 58.93% | 52925 | 58.94% | 211 | 57.18% | |
| Missing data | 46 | 0.05% | 46 | 0.05% | 0 | 0.00% | |
| Marital status | Married | 85583 | 94.92% | 85229 | 94.92% | 354 | 95.93% |
| Single | 3113 | 3.45% | 3104 | 3.46% | 9 | 2.44% | |
| Divorce | 738 | 0.82% | 735 | 0.82% | 3 | 0.81% | |
| Widow | 14 | 0.02% | 14 | 0.02% | 0 | 0.00% | |
| Missing data | 715 | 0.79% | 712 | 0.79% | 3 | 0.81% | |
| Education | ≤12 years | 32560 | 36.11% | 32431 | 36.12% | 129 | 34.96% |
| ≥13 years | 56494 | 62.66% | 56258 | 62.65% | 236 | 63.96% | |
| Missing data | 1109 | 1.23% | 1105 | 1.23% | 4 | 1.08% | |
| Occupation | Fulltime, house business, temporal staff |
33973 | 37.68% | 33828 | 37.67% | 145 | 39.30% |
| Part time, others | 20902 | 23.18% | 20818 | 23.18% | 84 | 22.76% | |
| Housewife | 33904 | 37.60% | 33769 | 37.61% | 135 | 36.59% | |
| Unemployment | 1249 | 1.39% | 1244 | 1.39% | 5 | 1.36% | |
| Missing data | 135 | 0.15% | 135 | 0.15% | 0 | 0.00% | |
| Smoking | Never | 52142 | 57.83% | 51936 | 57.84% | 206 | 55.83% |
| Quit before conception | 21358 | 23.69% | 21266 | 23.68% | 92 | 24.93% | |
| Quit after conception | 12068 | 13.38% | 12023 | 13.39% | 45 | 12.20% | |
| Smoking | 4429 | 4.91% | 4403 | 4.90% | 26 | 7.05% | |
| Missing data | 166 | 0.18% | 166 | 0.18% | 0 | 0.00% | |
| Alcohol | Never | 31149 | 34.55% | 31011 | 34.54% | 138 | 37.40% |
| Quit | 50026 | 55.48% | 49828 | 55.49% | 198 | 53.66% | |
| Almost none | 1073 | 1.19% | 1068 | 1.19% | 5 | 1.36% | |
| Drink | 7880 | 8.74% | 7852 | 8.74% | 28 | 7.59% | |
| Missing data | 35 | 0.04% | 35 | 0.04% | 0 | 0.00% | |
| Folate supplementation | Less than once/week | 50629 | 56.15% | 50421 | 56.15% | 208 | 56.37% |
| More than once/week | 14280 | 15.84% | 14210 | 15.83% | 70 | 18.97% | |
| Everyday | 25235 | 27.99% | 25144 | 28.00% | 91 | 24.66% | |
| Missing data | 19 | 0.02% | 19 | 0.02% | 0 | 0.00% | |
| Assisted Reproductive Technology | Yes | 7579 | 8.41% | 7536 | 8.39% | 43 | 11.65% |
| No | 81850 | 90.78% | 81526 | 90.79% | 324 | 87.80% | |
| Missing data | 734 | 0.81% | 732 | 0.82% | 2 | 0.54% | |
| Maternal medical drug usage during pregnancy | Yes | 79433 | 88.10% | 79101 | 88.09% | 332 | 89.97% |
| No | 9973 | 11.06% | 9938 | 11.07% | 35 | 9.49% | |
| Missing data | 757 | 0.84% | 755 | 0.84% | 2 | 0.54% | |
| Mode of delivery | Vaginal | 73468 | 81.48% | 73178 | 81.50% | 290 | 78.59% |
| C-section | 16462 | 18.26% | 16384 | 18.25% | 78 | 21.14% | |
| Missing data | 233 | 0.26% | 232 | 0.26% | 1 | 0.27% | |
| Household Income | ≤2 million | 4739 | 5.26% | 4722 | 5.26% | 17 | 4.61% |
| 2 to <4 | 28928 | 32.08% | 28816 | 32.09% | 112 | 30.35% | |
| 4 to <6 | 27453 | 30.45% | 27337 | 30.44% | 116 | 31.44% | |
| 6 to <8 | 13151 | 14.59% | 13091 | 14.58% | 60 | 16.26% | |
| 8 to <10 | 5368 | 5.95% | 5353 | 5.96% | 15 | 4.07% | |
| 10+ | 3521 | 3.91% | 3504 | 3.90% | 17 | 4.61% | |
| Missing data | 7003 | 7.77% | 6971 | 7.76% | 32 | 8.67% | |
|
| |||||||
| Father | |||||||
| Smoking | Never | 24124 | 26.76% | 24027 | 26.76% | 97 | 26.29% |
| Quit before conception | 20790 | 23.06% | 20699 | 23.05% | 91 | 24.66% | |
| Quit after conception | 2237 | 2.48% | 2230 | 2.48% | 7 | 1.90% | |
| Smoking | 42354 | 46.97% | 42181 | 46.98% | 173 | 46.88% | |
| Missing data | 658 | 0.73% | 657 | 0.73% | 1 | 0.27% | |
| Education | ≤12 years | 39309 | 43.60% | 39138 | 43.59% | 171 | 46.34% |
| ≥13 years | 49187 | 54.55% | 48995 | 54.56% | 192 | 52.03% | |
| Missing data | 1667 | 1.85% | 1661 | 1.85% | 6 | 1.63% | |
|
| |||||||
| Infant | |||||||
| Child sex | Boys | 44232 | 49.06% | 44066 | 49.07% | 166 | 44.99% |
| Girls | 45927 | 50.94% | 45724 | 50.92% | 203 | 55.01% | |
| Missing data | 4 | 0.00% | 4 | 0.00% | 0 | 0.00% | |
| Gestational week | ≥37 | 86392 | 95.82% | 86048 | 95.83% | 344 | 93.22% |
| <37 | 3733 | 4.14% | 3708 | 4.13% | 25 | 6.78% | |
| Missing data | 38 | 0.04% | 38 | 0.04% | 0 | 0.00% | |
| Mean | ±SD | Mean | ±SD | Mean | ±SD | ||
| Birth weight | n = 90076 | 3034.49 | 401.41 | 3034.78 | 401.05 | 2962.11 | 476.61 |
| Birth height | n = 89858 | 48.98 | 2.16 | 48.98 | 2.16 | 48.56 | 2.72 |
| Birth head circumference | n = 89701 | 33.21 | 1.45 | 33.21 | 1.45 | 33.10 | 1.57 |
| Birth chest circumference | n = 89676 | 31.81 | 1.74 | 31.81 | 1.74 | 31.55 | 2.28 |