Table 4.
Baseline characteristics of paired data of pregnant women and their children in the JECS-A cohort
| Sub-cohort | |||||
| A1 | A2 | A3 | B | C | |
| Pregnant women (n) | 3426 | 2924 | 1753 | 1352 | 1187 |
| Age at delivery | |||||
| Mean | 31.6 | 31.7 | 31.8 | 31.8 | 32.0 |
| SD | 4.9 | 4.9 | 5.0 | 4.8 | 4.7 |
| Missing (n) | 44 | 14 | 7 | 0 | 0 |
| Smoking habits | |||||
| Never smoked (%) | 62.8 | 63.7 | 63.7 | 64.2 | 64.6 |
| Ex-smokers who quit before pregnancy | 21.6 | 22.0 | 23.1 | 21.8 | 23.1 |
| Smokers during early pregnancy | 9.0 | 9.0 | 8.3 | 8.4 | 7.8 |
| Smokers | 2.5 | 2.5 | 2.1 | 2.8 | 2.1 |
| Missing (n) | 144 | 82 | 51 | 38 | 29 |
| Secondhand smoking | |||||
| Rarely (%) | 67.5 | 69.1 | 69.6 | 68.6 | 71.9 |
| A few days a week | 18.6 | 18.6 | 18.0 | 19.1 | 17.1 |
| Daily | 10.4 | 10.1 | 10.3 | 10.1 | 9.6 |
| Missing (n) | 124 | 66 | 36 | 30 | 17 |
| Household income (JPY) | |||||
| <2000 (%) | 2.3 | 2.1 | 2.5 | 1.8 | 2.1 |
| 2000 to <4000 | 25.8 | 26.0 | 25.6 | 24.4 | 24.3 |
| 4000 to <6000 | 33.4 | 33.7 | 34.2 | 35.1 | 35.9 |
| 6000 to <8000 | 17.5 | 18.1 | 17.5 | 18.6 | 18.6 |
| 8000 to <10 000 | 7.3 | 7.5 | 7.8 | 7.5 | 8.3 |
| ≥10 000 | 4.5 | 4.7 | 4.5 | 3.9 | 4.5 |
| Missing (n) | 314 | 233 | 141 | 116 | 76 |
| Children (n)* | 3336 | 2884 | 1726 | 1346 | 1182 |
| Sex (singleton births) | |||||
| Male (%) | 50.5 | 50.4 | 50.1 | 49.9 | 50.4 |
| Female | 49.5 | 49.6 | 49.9 | 50.1 | 49.6 |
| Missing (n) | 0 | 0 | 0 | 0 | 0 |
| Birth weight, g (singleton births) | |||||
| Mean | 3041.6 | 3052.3 | 3054.1 | 3039.1 | 3062.7 |
| SD | 432.8 | 419.9 | 430.4 | 410.0 | 416.7 |
| Missing (n) | 22 | 15 | 9 | 4 | 6 |
| Birth height, cm (singleton births) | |||||
| Mean | 49.6 | 49.7 | 49.7 | 49.7 | 49.7 |
| SD | 2.3 | 2.2 | 2.2 | 2.1 | 2.1 |
| Missing (n) | 28 | 18 | 11 | 6 | 7 |
Sub - cohort A1, agreement on the adjunct questionnaire survey only; sub-cohort A2, agreement on the adjunct questionnaire survey and provision of mother’s biological specimen (blood and urine); sub-cohort A3, agreement on the adjunct questionnaire survey and provision of mother’s biological specimen (blood and urine) with genetic analysis; sub-cohort B, informed consent obtained for anthropometry measurement on child hands from guardians (legally acceptable representatives); sub-cohort C, informed consent obtained for provision of child’s biological specimen from guardian (legally acceptable representatives). JPY: Japanese yen, 110 JPY=1 US$ as of 2019.
*Multiple births (twin pairs) were excluded; A1: 20 (n=40), A2: 16 (n=32), A3: 12 (n=24), B: 5 (n=10) and C: 6 (n=12).
JECS-A, The Aichi regional sub-cohort of the Japan Environment and Children’s Study.