Table 1.
Baseline characteristics of participants according to percentile of birthweight
| Birthweight corrected for gestational age† | Percentile | All | |||
|---|---|---|---|---|---|
| <25 percentile (z‐score < −0.67) | 25–49 percentile (−0.67 ≤ z‐score < 0) | 50–74 percentile (0 ≤ z‐score < 0.67) | 75 percentile ≤ (0.67 ≤ z‐score) | ||
| No. participants (%) | 4,292 (24.7) | 4,864 (28.0) | 4,054 (23.3) | 4,188 (24.1) | 17,398 (100.0) |
| Mean age at survey, years (SD) | 40.9 (7.1) | 41.4 (7.3) | 39.0 (6.4) | 38.6 (6.6) | 40.0 (7.0)* |
| Mean birthweight, g (SD) | 2,559 (264) | 2,921 (179) | 3,088 (237) | 3,460 (393) | 3,000 (423)* |
| Range of birthweight (g) | 900–2,920 | 1,350–3,180 | 1,180–3,440 | 1,100–4,350 | 900–4,350 |
| Mean gestational age, weeks (SD) | 39.7 (1.5) | 39.8 (1.3) | 39.5 (1.5) | 39.3 (1.9) | 39.6 (1.6) |
| Mean BMI at age 18 years (SD) | 20.7 (2.4) | 21.0 (2.4) | 21.1 (2.4) | 21.3 (2.5) | 21.0 (2.4)* |
| Mean current BMI (SD) | 21.8 (3.1) | 21.9 (3.0) | 21.8 (3.1) | 21.9 (3.1) | 21.8 (3.1) |
| Mean z‐score of BMI at age 18 years (SD) | −0.02 (0.81) | 0.07 (0.81) | 0.11 (0.82) | 0.18 (0.85) | 0.08 (0.83)* |
| Mean z‐score of current BMI (SD) | −0.03 (0.94) | −0.01 (0.91) | 0.05 (0.95) | 0.09 (0.96) | 0.02 (0.94)* |
| History of adult‐onset diabetes (%) | 1.5 | 1.0 | 0.8 | 0.7 | 1.0* |
| History of father having diabetes (%) | 14.0 | 13.1 | 13.2 | 12.4 | 13.2 |
| History of mother having diabetes (%) | 7.8 | 8.0 | 7.6 | 9.3 | 8.2* |
*Significant trend according to percentile categories (P < 0.05). †The z‐score of birthweight was calculated based on the fetal growth curve for the Japanese general population (Unno, N. 2012). The z‐scores of −0.67, 0 and +0.67 correspond to the 25th, 50th and 75th percentiles, respectively. Note that the ranges of birthweight in the four categories overlapped, because the birthweight was corrected for gestational age. Note that the ranges of current BMI in the four categories were not consecutive, because the z‐score calculation was carried out according to age groups. BMI, body mass index; SD, standard deviation.