Table 3.

Unadjusted and adjusted odds ratios^* (95% CI) of preterm delivery among parity 0 women

Age group (years)	N	Preterm n (%)	Crude OR (95% CI)	Adjusted† OR (95% CI)
12−14	33	8 (24.4)	2.80 (0.72−10.93)	2.34 (0.57−9.53)
15−16	196	46 (23.5)	2.68 (0.89−8.13)	2.74 (0.94−8.03)
17−18	288	61 (21.2)	2.35 (0.77−7.17)	2.56 (0.87−7.50)
19−20	144	19 (13.2)	1.33 (0.41−4.27)	1.54 (0.49−4.81)
21−22	59	4 (6.8)	0.64 (0.15−2.72)	0.82 (0.20−3.44)
23−25	39	4 (10.3)	Reference	Reference

^*Odds ratios calculated using logistic regression with confidence intervals calculated using a robust estimation of the variance.

^†Adjusted for ethnicity, BMI, height, literacy and smoking. BMI, body mass index.