Table 4.
Adjusted risk ratios (RR) and 95% confidence intervals (CI) for associations between prenatal risk factors and preterm birth (PTB).
| Risk factors during pregnancy | Preterm birth (n = 36,044) RR (95% CI) |
|---|---|
| Pre-pregnancy BMI (kg) | |
| < 18.5 (low body weight) | |
| 18.5–23.9 (normal body weight) | 0.99 (0.94, 1.04) |
| 24-27.9 (Overweight) | 1.00 |
| 28 (obese) | 1.29 (1.25, 1.33) |
| GWG (Chinese standard) | 1.72 (1.66, 1.78) |
| Insufficient weight gain | |
| Proper weight gain | 1.74 (1.61, 1.88) |
| Excessive weight gain | 1.00 |
| HDP | 0.72 (0.69, 0.76) |
| Health | |
| Pregnancy complicated with chronic hypertension | 1.00 |
| CH concurrent preeclampsia | 2.16 (2.04, 2.29) |
| Hypertension of pregnancy | 2.72 (2.38, 3.12) |
| Preeclampsia | 1.63 (1.55, 1.72) |
| Fasting blood glucose in early pregnancy | 2.63 (2.40, 2.88) |
| Glucopenia | |
| Euglycemia | 1.06 (1.00, 1.12) |
| Hyperglycaemia | 1.00 |
| Early pregnancy fasting urine sugar | 1.19 (1.15, 1.22) |
| The urine sugar is normal | |
| Urine sugar is high | 1.00 |
| Hemoglobin in early pregnancy | 1.66 (1.50, 1.82) |
| Hemoglobin is too low | |
| Hemoglobin was normal | 1.05 (1.01, 1.10) |
| Folate supplementation in early pregnancy | 1.00 |
| Yes | |
| Deny | 1.00 |
| Assisted reproduction | 0.98 (0.96, 1.00) |
| Yes | |
| Deny | 3.39 (3.01, 3.83) |
| Exposure of teratogens | 1.00 |
| Yes | |
| Deny | 1.10 (1.02, 1.19) |
PTB preterm birth, RR risk ratio, CI confidence interval.