Table 1.
Maternal background according to pre-pregnancy body mass index based on 2009 IOM guidelines and Japanese criteria28.
| Group | GA | GB | GC | GD | P value | |
|---|---|---|---|---|---|---|
| BMI category (kg/m2) | < 18.5 | 18.5–< 25.0 | 25.0–< 30.0 | ≥ 30.0 | ||
| No. patients | 10,935 (15.2%) | 52,903 (73.7%) | 6072 (8.5%) | 1889 (2.6%) | ||
| Maternal background | ||||||
| Maternal age (years), % | ||||||
| < 20 | 0.9 | 0.5 | 0.5 | 0.3 | < 0.001 | |
| 20–29 | 41.9 | 34.9 | 32.0 | 31.6 | ||
| > 30 | 57.2 | 64.5 | 67.6 | 68.2 | ||
| Maternal education (years), % | ||||||
| < 10 | 5.1 | 4.0 | 6.0 | 8.9 | < 0.001 | |
| 10–12 | 30.9 | 29.9 | 38.0 | 43.5 | ||
| 13–16 | 62.5 | 64.6 | 54.9 | 47.0 | ||
| > 17 | 1.5 | 1.4 | 1.1 | 0.5 | ||
| Annual household income (JPY), % | ||||||
| < 2,000,000 | 6.0 | 5.2 | 7.6 | 10.3 | < 0.001 | |
| 2,000,000–5,999,999 | 67.3 | 67.1 | 70.4 | 72.6 | ||
| 6,000,000–9,999,999 | 22.1 | 23.3 | 18.6 | 15.0 | ||
| > 10,000,000 | 4.6 | 4.4 | 3.4 | 2.1 | ||
| Smoking during pregnancy, % | 5.0 | 4.2 | 6.5 | 7.8 | < 0.001 | |
| Primiparous, % | 43.4 | 40.1 | 34.4 | 34.0 | < 0.001 | |
| Obstetrics outcomes | ||||||
| Gestational age, week (mean ± SD) | 38.7 (1.5) | 38.9 (1.5) | 38.8 (1.6) | 38.6 (1.9) | < 0.001 | |
| PTB before 37 weeks, % | 5.0 | 4.0 | 5.5 | 7.3 | < 0.001 | |
| Birth weight, g (mean ± SD) | 2925 (388) | 3038 (401) | 3115 (454) | 3157 (508) | < 0.001 | |
| SGA infants, % | 7.3 | 4.6 | 4.0 | 3.3 | < 0.001 | |
| Gestational weight gain, kg (mean ± SD) | 10.8 (3.5) | 10.5 (3.8) | 8.6 (10.0) | 5.2 (5.7) | < 0.001 | |
| Caesarean delivery, % (n) | 14.8 (1614) | 18.0 (9506) | 27.3 (1657) | 35.8 (677) | < 0.001 | |
| UmA-pH < 7.2, % | 6.2 | 6.2 | 6.9 | 7.5 | 0.037 | |
| UmA-pH < 7.1, % | 1.1 | 1.2 | 1.3 | 1.3 | 0.554 | |
| Group | G1 | G2 | G3 | G4 | G5 | P value |
|---|---|---|---|---|---|---|
| BMI category (kg/m2) | < 18.5 | 18.5–< 20.0 | 20–< 23.0 | 23.0–< 25.0 | ≥ 25 | |
| No. patients |
10,935 (15.2%) |
17,418 (24.3%) |
27,835 (38.8%) |
7650 (10.7%) |
7961 (11.1%) |
|
| Maternal background | ||||||
| Maternal age (years), % | ||||||
| < 20 | 0.9 | 0.7 | 0.5 | 0.3 | 0.4 | < 0.001 |
| 20–29 | 41.9 | 36.8 | 34.6 | 31.9 | 31.9 | |
| > 30 | 57.2 | 62.6 | 64.9 | 67.8 | 67.7 | |
| Maternal education (years), % | ||||||
| < 10 | 5.1 | 3.8 | 3.9 | 4.4 | 6.7 | < 0.001 |
| 10–12 | 30.9 | 28.5 | 29.8 | 33.7 | 39.3 | |
| 13–16 | 62.5 | 66.1 | 64.8 | 60.8 | 53.0 | |
| > 17 | 1.5 | 1.6 | 1.4 | 1.2 | 1.0 | |
| Annual household income, % | ||||||
| < 2,000,000 | 6.0 | 5.0 | 5.1 | 6.0 | 8.2 | < 0.001 |
| 2,000,000–5,999,999 | 67.3 | 65.6 | 67.3 | 69.7 | 70.9 | |
| 6,000,000–9,999,999 | 22.1 | 24.3 | 23.3 | 21.2 | 17.8 | |
| > 10,000,000 | 4.6 | 5.0 | 4.4 | 3.0 | 3.1 | |
| Smoking during pregnancy, % | 5.0 | 3.9 | 4.1 | 4.9 | 6.8 | < 0.001 |
| Primiparous, % | 43.4 | 42.6 | 39.4 | 36.6 | 34.3 | < 0.001 |
| Obstetrics outcomes | ||||||
| Gestational age, week (mean ± SD) | 38.7 (1.5) | 38.9 (1.4) | 38.9 (1.5) | 38.9 (1.5) | 38.8 (1.7) | < 0.001 |
| PTB before 37 weeks, % | 5.0 | 4.0 | 4.0 | 4.2 | 5.9 | < 0.001 |
| Birth weight, g (mean ± SD) | 2925 (388) | 2997 (387) | 3049 (401) | 3095 (421) | 3125 (467) | < 0.001 |
| SGA infants, % | 7.3 | 5.4 | 4.4 | 3.8 | 3.8 | < 0.001 |
| Gestational weight gain, kg (mean ± SD) | 10.8 (3.5) | 10.7 (3.5) | 10.6 (3.8) | 10.0 (4.4) | 7.8 (9.3) | < 0.001 |
| Caesarean delivery, % (n) | 14.8 (1614) | 15.3 (2666) | 18.4 (5132) | 22.3 (1708) | 29.3 (2334) | < 0.001 |
| UmA-pH < 7.2, % | 6.2 | 5.9 | 6.4 | 6.4 | 7.0 | 0.014 |
| UmA-pH < 7.1, % | 1.1 | 1.1 | 1.2 | 1.2 | 1.3 | 0.355 |
One-way analysis of variance, Kruskal-Wallis test and the Chi-square test were used to compare continuous and categorical variables, respectively. BMI body mass index, G1 group 1, G2 group 2, G3 group 3, G4 group 4, G5 group 5, GA group A, GB group B, GC group C, GD group D, IOM Institute of Medicine, JPY Japanese yen, PTB preterm birth, SGA small-for-gestational age, UmA-pH umbilical artery pH.