Plasma C-reactive protein in early pregnancy and preterm delivery

Abstract

Systemic maternal infections have been associated with preterm delivery. The authors examined the association of C-reactive protein (CRP), a marker of inflammation, with preterm delivery. This nested case-control study was conducted within Project Viva in Massachusetts between 1999 and 2002. Subjects were 117 women who delivered preterm (< 37 weeks' gestation) and 117 controls (term deliveries) matched on age, race/ethnicity, and smoking status. High-sensitivity CRP assays were performed on early-pregnancy (5.3-19.3 weeks' gestation) plasma samples. Odds ratios and 95% confidence intervals were estimated by using conditional logistic regression adjusted for matching factors, gestational age at blood collection, and prepregnancy body mass index. Median concentration of CRP was 3.2 mg/liter in cases versus 2.4 mg/liter in controls. No significant association was found between quartiles of CRP and preterm delivery. However, CRP levels exceeding the threshold defined in the literature were associated with increased risk of preterm delivery (odds ratio = 2.55, 95% confidence interval: 1.05, 6.02 for CRP > or = 8 mg/liter). The association was stronger among cases who experienced spontaneous delivery (odds ratio = 4.64, 95% confidence interval: 0.94, 22.96) versus indicated delivery (odds ratio = 1.42, 95% confidence interval: 0.44, 4.61). These findings suggest that very high CRP levels in early pregnancy are associated with preterm delivery.

FIGURE 1

Distribution of C-reactive protein according to gestational age at delivery, Project Viva, Massachusetts, 1999–2003. The boxes represent the interquartile range; the lower edge and upper edge correspond to the 25th and 75th percentiles, respectively. The horizontal line in each box represents the median level of C-reactive protein in each group. The extreme values within 1.5 times the interquartile range from the upper or lower quartile are the ends of the lines extending from the boxes.