Table 3

The “social gradient in preterm birth”; risk of preterm birth among decile 10 women compared to decile 1 women (same year), New Zealand singleton live births 1980, 1990, and 1999

Gestational age category
All preterm20–28 wk** (n=2693)29–32 wk (n=12669)33–36 wk (n=36266)
YearOR*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.
19801.671.281.661.48
19901.501.371.471.32
19991.371.461.321.19