C-reactive protein levels at the onset of labour and at day 3 post-partum in normal pregnancy.

OBJECTIVES

To record maternal serum C-reactive protein levels during normal onset of labour and normal puerperium and to evaluate if inflammation or infection could be predicted during these two periods when serum C-reactive protein is increased.

METHODS

Eighty-five pregnant women were enrolled in a longitudinal prospective study and had a blood sample to assess serum C-reactive protein levels on admission to the labour ward for normal onset of labour and at day three post-partum. Inclusion criteria were no previous history, a normal single pregnancy, normal vaginal delivery and an uneventful post-partum course. Twelve non-pregnant women of the same age constitued a control group. An automatic Behring Nephelometer was used to measure serum C-reactive protein concentrations. The Student's t-test (significance p < 0.05) was used for statistical analysis.

FINDINGS

C-reactive protein was significantly increased during the onset of labour (4.10 +/- 2.79 mg/L) and reached very high levels during the post-partum period (24.07 +/- 18.28 mg/L) compared to the standard normal serum C-reactive protein level in a population of non-pregnant women of the same age (2.39 +/- 0.07 mg/L).

INTERPRETATION

Increased serum C-reactive protein has been reported to be a marker for subclinical infection during pregnancy in various situations including premature labour and premature rupture of membranes and for complications occurring during puerperium such as thrombophlebitis, thromboembolism or endometritis. This interpretation depends on which upper limit is considered as abnormal. Because serum C-reactive protein was raised during the onset of labour, values of less than 10 mg/L could not be considered as a marker for infection during this period. Elevated serum concentrations of estrogen, progestogen and prostaglandins during labour might be one explanation for those physiological changes. Normal vaginal delivery could be compared to a surgical procedure and tissue injury consecutive to vaginal birth as reflected by a dramatic increase in C-reactive protein. More studies using nephelometry are needed to determine normal and upper values of C-reactive protein during pregnancy.