Gestational age category | ||||
---|---|---|---|---|
All preterm | 20–28 wk** (n=2693) | 29–32 wk (n=12669) | 33–36 wk (n=36266) | |
Year | OR* | OR* | OR* | OR* |
Multivariate analysis adjusted for gender, maternal age, parity, birth year, decile, and birth year*decile, year*age, year*parity, decile*age, decile*parity. | ||||
*Odds ratios for preterm birth among decile 10 women compared to those in decile 1 for each particular year reflects to social gradient for that year. | ||||
**Odds ratios for the 20–28 week category did not reach statistical significance. | ||||
1980 | 1.67 | 1.28 | 1.66 | 1.48 |
1990 | 1.50 | 1.37 | 1.47 | 1.32 |
1999 | 1.37 | 1.46 | 1.32 | 1.19 |