Table 2.
Regression analysis identifying factors associated with preterm birth in Hubei Province, China (2001 – 2012)
| Covariates | Univariate analysis OR (95 % CI) |
Multivariable analysis* OR (95 % CI) |
|---|---|---|
| Year | 1.01 (1.00 - 1.01) | ---- |
| Maternal age (<35 y vs. ≥ 35 y) | 5.28 (5.04 - 5.45) | 0.57(0.55-0.58) |
| Gestational week(<34 week vs. ≥ 34 week) | 2.21 (1.86 - 2.63) | ---- |
| Birth weight(<2.5 kg vs. ≥ 2.5 kg) | 1.08 (1.05 -1.13) | ---- |
| Pregnancy parity(1 vs. ≥ 2) | 2.80 (2.69 - 2.95) | ---- |
| Birth parity (1 vs. ≥ 2) | 1.08 (1.01 - 1.10) | ---- |
| Assisted reproductive technology (yes vs. no) |
1.97 (1.91 -2.05) | 3.67 (3.56-3.78) |
| Income (<500 USD/month vs. ≥ 500 USD/month) | 1.27 (1.22- 1.32) | 0.63 (0.61-0.66) |
| Education (>9 years vs. ≤ 9 years) | 0.71 (0.49 - 0.91) | 1.04 (1.01-1.06) |
| Residence (rural vs. urban) | 1.37 (1.35 - 1.39) | 1.27 (1.24-1.30) |
| Newborn Emergency Transport Service (yes vs. no) | 3.13 (3.02 - 3.23) | ---- |
| Infant gender (female vs. male) | 0.59 ( 0.56 - 0.63) | 3.31 (3.23 -3.39) |
| Occupation (physical labor vs. office job) | 2.16 (2.09 - 2.23) | ---- |
| Single birth | 0.91 (0.89 - 0.97) | ---- |
*Multivariate logistic model was fit with all characteristics considered as predictors of preterm birth, and a backward-selection procedure was used to select significant variables included in the final model, with a P value < 0.05 indicating significance