Table 2.

Odds ratio and 95% CI of preterm delivery according to maternal serum C-reactive protein concentrations measured in early pregnancy, Seattle and Tacoma, WA, 1996-2002

	Control		Preterm cases
	(n = 1,623)		(n = 146)		Unadjusted OR		Adjusted OR*
C-Reactive Protein (mg/l)	n	%	n	%	(95% CI)		(95% CI)
Quartile 1 (<2.0)	388	23.9	26	17.8	1.00	Reference	1.00	Reference
Quartile 2 (2.0-3.9)	385	23.7	35	24.0	1.36	(0.80-2.30)	1.44	(0.82-2.53)
Quartile 3 (4.0-7.4)	391	24.1	28	19.2	1.07	(0.62-1.86)	1.29	(0.72-2.32)
Quartile 4 (≥ 7.5)	389	24.0	49	33.6	1.88	(1.15-3.09)	2.04	(1.13-3.69)
Missing	70	4.3	8	5.5
Trend test p-value						0.027		0.033

^*Adjusted for maternal age, race, parity, pre-pregnancy body mass index and gestational age at blood collection 70 controls and 8 cases were not included in the analysis of CRP because of missing data.