Table 1 Maternal characteristics and obstetric outcomes by pre-pregnancy BMI.
Maternal characteristics | BMI category (kg/m2) | P | ||||
|---|---|---|---|---|---|---|
G1 | G2 | G3 | G4 | G5 | ||
< 18.5 | 18.5 to < 20.0 | 20 to < 23.0 | 23.0 to < 25.0 | ≥ 25.0 | ||
n = 10,935 | n = 17,418 | n = 27,835 | n = 7650 | n = 7961 | ||
Maternal age, % | ||||||
< 20 years | 0.9 | 0.7 | 0.5 | 0.3 | 0.4 | < 0.001 |
20 to 29 years | 41.9 | 36.8 | 34.6 | 31.9 | 31.9 | |
> 30 years | 57.2 | 62.6 | 64.9 | 67.8 | 67.7 | |
Maternal education, % | ||||||
< 10 years | 5.1 | 3.8 | 3.9 | 4.4 | 6.7 | < 0.001 |
10 to 12 years | 30.9 | 28.5 | 29.8 | 33.7 | 39.3 | |
13 to 16 years | 62.5 | 66.1 | 64.8 | 60.8 | 53.0 | |
> 17 years | 1.5 | 1.6 | 1.4 | 1.2 | 1.0 | |
Annual household income, % | ||||||
< 2,000,000 JPY | 6.0 | 5.0 | 5.1 | 6.0 | 8.2 | < 0.001 |
2,000,000–5,999,999 JPY | 67.3 | 65.6 | 67.3 | 69.7 | 70.9 | |
6,000,000–9,999,999 JPY | 22.1 | 24.3 | 23.3 | 21.2 | 17.8 | |
> 10,000,000 JPY | 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 |
Nulliparous, % | 43.4 | 42.6 | 39.4 | 36.6 | 34.3 | < 0.001 |
Caesarean delivery, % | 14.8 | 15.3 | 18.4 | 22.3 | 29.3 | < 0.001 |
Obstetric outcomes | ||||||
Gestational age, weeks (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 |
UmA-pH < 7.20, % | 6.2 | 5.9 | 6.4 | 6.4 | 7.0 | 0.014 |
UmA-pH < 7.10, % | 1.1 | 1.1 | 1.2 | 1.2 | 1.3 | 0.355 |
