Background: C-reactive protein (CRP) is an acute-phase reactant, and the CRP level has been reported to be slightly elevated in pregnant women. Although CRP has been extensively studied in early pregnancy, mid-pregnancy, and preterm premature rupture of the membranes (ROM), maternal CRP at term is insufficiently studied. This study aimed to analyze maternal CRP values and its relation to neonatal infection in term labor and delivery.Materials and methods: Data of pregnant women who delivered their babies at our clinic were retrospectively collected. The enrollment criteria were; ≥37 weeks of gestation, and live singleton pregnancy. Maternal CRP level was measured at admission, and repeated daily until delivery. The women were classified into three groups: A, admission for induction/planned cesarean section; B, admission for labor onset with or without ROM; and C, admission for ROM without labor.Results: A total of 4612 women (2133 nulliparas and 2479 multiparas) were enrolled. CRP levels at admission were higher in nulliparas than in multiparas (median [10th percentile, 90th percentile ]: 0.2 [0.0, 1.3] vs. 0.1 [0.0, 0.8], p<0.001). In nulliparas, CRP at admission was higher in group B (0.2 [0.0, 1.5]) than in groups A (0.2 [0.0, 0.7] and group C (0.1 [0.0, 0.8]) (both p<0.001). In multiparas, such difference was not observed. CRP levels were significantly higher on the delivery day than those at admission in both nulliparas and multiparas. A higher rate of neonatal care unit admission for infection and/or respiratory problems was observed in babies of women with elevated CRP (≥1.0mg/dl) than in babies of women without CRP elevation (30/804 vs. 37/3808, p<0.001, odds ratio 3.95).
Conclusion:Maternal CRP levels may differ according to the indication for admission in nulliparous women. CRP levels increase during labor, and neonates of mothers with high CRP levels should be carefully observed for infection and respiratory problems.