No clear evidence exists to support the use of C-reactive protein (CRP) for the early diagnosis of chorioamnionitis following preterm prelabor rupture of membranes, according to a systematic review from the United Kingdom. 

Researchers reviewed eight studies including 610 cases and found wide variation in the results. Three of the studies concluded that CRP was diagnostically useful, although one suggested using a higher CRP threshold (30, 35, or 40 mg/L for single estimations or >20 mg/L for serial estimations), while the remaining studies concluded that CRP as a diagnostic tool for chorioamnionitis was poor.  

Part of the problem is the disagreement about what CRP values are normal during pregnancy and whether concentrations should increase as pregnancy progresses. While the use of serial measurements of CRP seems promising, it requires further investigation.  