Table 1. Characteristics of study participants among 38 539 mother-infant pairs according to gestational weight gain categories in Tianjin, China.
| Pre-pregnancy BMI (kg/m2) |
P for trend | IOM categories § |
P for trend | ||||||
|---|---|---|---|---|---|---|---|---|---|
| <18.5 | 18.5-23.99 | 24.0-27.99 | ≥28 | Inadequate | Adequate | Excessive | |||
| No. of subjects | 4 255 | 24 678 | 7 186 | 2 420 | 3 793 | 12 645 | 22 101 | ||
| Maternal characteristics | |||||||||
| Gestational weight gain, kg | 16.5 (5.1) | 17.7 (5.5) | 18.0 (6.2) | 17.2 (6.9) | <0.001 | 9.4 (1.9) | 14.3 (1.8) | 20.9 (5.1) | <0.001 |
| Maternal age before pregnancy, y | 26.7 (2.9) | 27.6 (3.2) | 28.1 (3.5) | 28.1 (3.6) | <0.001 | 27.8 (3.7) | 27.8 (3.3) | 27.5 (3.2) | <0.001 |
| Gestational age at delivery, wk | 39.2 (1.1) | 39.3 (1.1) | 39.2 (1.2) | 38.1 (1.2) | <0.001 | 39.2 (1.1) | 39.2 (1.1) | 39.3 (1.1) | <0.001 |
| Prepregnancy BMI, kg/m2 | 17.6 (0.8) | 21.1 (1.5) | 25.6 (1.1) | 30.6 (2.4) | <0.001 | 20.5 (2.4) | 20.9 (2.5) | 23.2 (3.7) | <0.001 |
| Mother’s education, % | <0.001 | <0.001 | |||||||
| University and above | 44.8 | 48.1 | 41.4 | 29.3 | 42.8 | 49.0 | 43.7 | ||
| Junior college | 28.5 | 26.8 | 27.8 | 27.2 | 25.5 | 26.1 | 28.1 | ||
| High school and under | 26.7 | 25.1 | 30.8 | 43.5 | 31.7 | 24.9 | 28.2 | ||
| Family income, yuan/month #, % | <0.001 | <0.001 | |||||||
| ≥3000 | 55.9 | 58.3 | 52.3 | 43.6 | 51.6 | 57.5 | 55.9 | ||
| 2000-2999 | 23.7 | 21.7 | 25.1 | 25.3 | 23.6 | 22.4 | 22.9 | ||
| <2000 | 20.4 | 20.0 | 22.6 | 31.1 | 24.8 | 20.1 | 21.2 | ||
| Smoking during pregnancy, % | 1.2 | 1.0 | 1.2 | 1.9 | <0.001 | 0.9 | 0.8 | 1.4 | <0.001 |
| Passive smoking, % | 48.3 | 48.1 | 50.2 | 54.5 | <0.001 | 46.5 | 46.4 | 50.7 | <0.001 |
| Occupation of mother, % | <0.001 | <0.001 | |||||||
| Farmers and workers | 15.9 | 16.7 | 19.9 | 25.1 | 18.2 | 16.5 | 18.3 | ||
| Office workers | 42.5 | 42.7 | 38.9 | 32.2 | 40.2 | 42.7 | 40.8 | ||
| Service professional workers | 19.1 | 21.0 | 19.6 | 16.3 | 18.6 | 21.3 | 19.9 | ||
| Unemployed persons | 10.1 | 8.4 | 9.5 | 12.6 | 10.5 | 8.4 | 9.2 | ||
| Other | 12.4 | 11.2 | 12.1 | 13.8 | 12.5 | 11.1 | 11.8 | ||
| Child characteristics | 0.159 | 0.106 | |||||||
| Boy, % | 50.0 | 51.6 | 51.8 | 52.4 | 52.2 | 50.8 | 51.8 | ||
| Mode of infant feeding, % | <0.001 | <0.001 | |||||||
| Exclusive breast-feeding | 15.1 | 15.3 | 14.0 | 11.3 | 14.9 | 16.0 | 14.1 | ||
| Mixed breast and formula | 68.8 | 70.8 | 70.8 | 68.5 | 70.5 | 70.2 | 70.5 | ||
| Weaned from breast-feeding | 14.1 | 12.1 | 12.6 | 17.3 | 12.7 | 12.0 | 13.2 | ||
| Exclusive formula feeding | 2.0 | 1.8 | 2.6 | 2.9 | 1.9 | 1.8 | 2.2 | ||
| Weight, kg | |||||||||
| Birth, gram | 3265 (388) | 3411 (413) | 3515 (453) | 3594 (489) | <0.001 | 3275 (399) | 3343 (398) | 3499 (438) | <0.001 |
| 3 month | 6.74 (0.77) | 6.96 (0.80) | 7.04 (0.81) | 7.07 (0.84) | <0.001 | 6.82 (0.79) | 6.88 (0.79) | 7.02 (0.81) | <0.001 |
| 6 month | 8.42 (0.96) | 8.69 (1.00) | 8.82 (1.04) | 8.90 (1.07) | <0.001 | 8.54 (0.99) | 8.60 (0.99) | 8.77 (1.03) | <0.001 |
| 9 month | 9.39 (1.03) | 9.70 (1.10) | 9.87 (1.15) | 9.94 (1.18) | <0.001 | 9.52 (1.09) | 9.60 (1.07) | 9.81 (1.13) | <0.001 |
| 12 month | 10.2 (1.1) | 10.5 (1.1) | 10.7 (1.2) | 10.8 (1.3) | <0.001 | 10.3 (1.1) | 10.4 (1.1) | 10.6 (1.2) | <0.001 |
| Length, cm | |||||||||
| Birth | 50.0 (1.4) | 50.3 (1.5) | 50.5 (1.5) | 50.6 (1.6) | <0.001 | 50.0 (1.4) | 50.1 (1.4) | 50.5 (1.5) | <0.001 |
| 3 month | 62.6 (2.2) | 63.0 (2.2) | 63.0 (2.3) | 63.0 (2.3) | <0.001 | 62.6 (2.2) | 62.8 (2.2) | 63.1 (2.2) | <0.001 |
| 6 month | 68.8 (2.4) | 69.2 (2.4) | 69.3 (2.5) | 69.2 (2.5) | <0.001 | 68.8 (2.5) | 69.0 (2.4) | 69.3 (2.4) | <0.001 |
| 9 month | 73.0 (2.5) | 73.4 (2.5) | 73.6 (2.6) | 73.5 (2.6) | <0.001 | 73.1 (2.5) | 73.3 (2.5) | 73.6 (2.6) | <0.001 |
| 12 month | 76.6 (2.6) | 77.0 (2.7) | 77.2 (2.7) | 77.2 (2.7) | <0.001 | 76.7 (2.6) | 76.8 (2.6) | 77.2 (2.7) | <0.001 |
| Overweight at age 12 months*, % | 29.2 | 38.2 | 44.5 | 48.4 | <0.001 | 33.1 | 35.7 | 41.9 | <0.001 |
| Obesity at age 12 months *, % | 12.3 | 18.6 | 23.5 | 27.1 | <0.001 | 15.2 | 17.0 | 21.4 | <0.001 |
BMI, body mass index.
# US$1=six point one yuan
* Overweight was defined as weight-for-length ≥85th percentile (≥1.035 Z score); Obesity was defined as weight-for-length ≥95th percentile (≥1.645 Z score); Sex-specific weight-for-length percentiles were based on WHO growth reference (World Health Organization, 2006).
§ IOM categories: Inadequate (1): <12.5 kg (pre-pregnancy BMI <18.5 kg/m2), <11.5 kg (BMI 18.5- 23.9 kg/m2), <7 kg (BMI 24.0–27.9 kg/m2), and <5 kg (BMI >28 kg/m2); Adequate (1): 12.5–18 kg (BMI <18.5 kg/m2), 11.5–16 kg (BMI 18.5- 23.9 kg/m2), 7–11.5 kg (BMI 24.0–27.9 kg/m2), and 5–9 kg (BMI >28 kg/m2); Excessive (1): >18 kg (BMI <18.5 kg/m2), >16 kg (BMI 18.5- 23.9 kg/m2), >11.5 kg (BMI 24.0–27.9 kg/m2), and >9 kg (BMI >28 kg/m2), according to the Chinese maternal pre-pregnancy BMI classification standard and the 2009 IOM GWG recommendations.