Table 2. Ratio of the odds of delivering an infant too small for gestational age relative to the odds of delivering an infant with appropriate size for gestational age as a function of maternal characteristics, infant sex and gestational age at delivery, Nha Trang, Viet Nam, 2007–2008.
| Characteristic | No.a/totalb (%) | Crude OR | 95% CI | P | Adjusted OR | 95% CI | P |
|---|---|---|---|---|---|---|---|
| Gestational weight gain (kg) | |||||||
| < 10 | 151/729 (20.7) | 2.08 | 1.63–2.64 | < 0.001 | 1.90 | 1.48–2.44 | < 0.001 |
| ≥ 10 but < 15 | 161/1405 (11.5) | 1.00 | – | 1.00 | – | ||
| ≥ 15 | 49/558 (8.8) | 0.68 | 0.49–0.95 | 0.024 | 0.74 | 0.52–1.05 | 0.086 |
| BMIc | |||||||
| Low | 141/742 (19.0) | 1.86 | 1.47–2.35 | < 0.001 | 1.95 | 1.52–2.50 | < 0.001 |
| Normal | 196/1749 (11.2) | 1.00 | – | 1.00 | – | ||
| High | 24/201 (11.9) | 1.07 | 0.68–1.69 | 0.755 | 0.95 | 0.60–1.52 | 0.844 |
| Maternal age (years) | |||||||
| < 24 | 136/812 (16.7) | 1.55 | 1.18–2.03 | 0.002 | 1.13 | 0.84–1.52 | 0.431 |
| 25–29 | 109/949 (11.5) | 1.00 | – | 1.00 | – | ||
| 30–34 | 67/587 (11.4) | 0.99 | 0.72–1.37 | 0.966 | 1.02 | 0.73–1.44 | 0.904 |
| ≥ 35 | 49/344 (14.2) | 1.28 | 0.89–1.84 | 0.182 | 1.24 | 0.84–1.82 | 0.281 |
| Parity | |||||||
| Primipara | 204/1400 (14.6) | 1.00 | – | 1.00 | – | ||
| Multipara | 157/1292 (12.2) | 0.81 | 0.65–1.01 | 0.066 | 0.78 | 0.60–1.02 | 0.073 |
| Income ( × 1 000 Vietnamese dong) | |||||||
| < 1 500 | 49/255 (19.2) | 1.26 | 0.88–1.80 | 0.201 | 1.08 | 0.75–1.56 | 0.688 |
| ≥ 1 500 but < 2 500 | 157/989 (15.9) | 1.00 | – | 1.00 | – | ||
| ≥ 2 500 but < 3 500 | 97/779 (12.5) | 0.75 | 0.57–0.99 | 0.042 | 0.85 | 0.64–1.13 | 0.271 |
| ≥ 3 500 | 58/669 (8.7) | 0.50 | 0.37–0.69 | < 0.001 | 0.67 | 0.48–0.95 | 0.025 |
| Education (years) | |||||||
| < 12 | 243/1506 (16.1) | 1.43 | 1.10–1.87 | 0.008 | 1.30 | 0.98–1.74 | 0.068 |
| 12 | 84/708 (11.9) | 1.00 | – | 1.00 | – | ||
| > 12 | 34/478 (7.1) | 0.57 | 0.38–0.86 | 0.008 | 0.67 | 0.43–1.04 | 0.071 |
| Total physical activitydin MET h/wk | |||||||
| < 25th percentile | 98/671 (14.6) | 0.96 | 0.71–1.30 | 0.797 | 0.89 | 0.65–1.22 | 0.460 |
| ≥ 25th but < 50th percentile | 103/681 (15.1) | 1.00 | – | 1.00 | – | ||
| ≥ 50th but < 75th percentile | 79/666 (11.9) | 0.76 | 0.55–1.04 | 0.082 | 0.88 | 0.64–1.23 | 0.460 |
| ≥ 75th percentile | 81/673 (12.0) | 0.77 | 0.56–1.05 | 0.100 | 0.98 | 0.70–1.35 | 0.878 |
| Smoking exposure | |||||||
| None | 215/1737 (12.4) | 1.00 | – | 1.00 | – | ||
| Passive indoor smoking | 146/955 (15.3) | 1.28 | 1.02–1.60 | 0.034 | 1.06 | 0.84–1.34 | 0.638 |
| Pre-eclampsia | 10/35 (28.6) | 2.63 | 1.25–5.52 | 0.011 | 3.14 | 1.43–6.90 | 0.004 |
| Infant sex (male = 1, female = 0) | 207/1419 (14.6) | 1.24 | 0.99–1.55 | 0.059 | 1.21 | 0.96–1.52 | 0.114 |
| Gestational age at delivery | – | 0.87e | 0.79–0.95 | 0.002 | 0.89 | 0.81–0.97 | 0.012 |
BMI, body mass index; CI, confidence interval; MET h/wk, metabolic equivalent hours per week; OR, odds ratio.
a This represents the number of infants too small for gestational age (n = 361) born to women with the characteristic.
b This figure represents the number of infants of appropriate size plus the number of infants too small for gestational age (n = 2692) born to women with the characteristic.
c BMI represents body weight in kilograms divided by body surface area in square metres. Categories: low BMI: < 18.5; normal BMI, ≥ 18.5 but < 23.0; high BMI, ≥ 23.0.
d There is one case with missing data for physical activity.
e The OR represents the change in the risk of delivering a small baby with each additional week of gestation.