Problem: Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine involved in reproduction. Presently there is no information on the possible involvement of MIF in the onset of labor.
Methods: Macrophage migration inhibitory factor was assayed, by enzyme-linked immunosorbent assay (ELISA), in maternal serum (MS) and amniotic fluid (AF) both, at midtrimester and at term, as well as in cord serum (CS) at birth. Extraembryonic membranes were analyzed by immunohistochemistry.
Results: Amniotic fluid MIF concentrations were significantly higher at term (median 62.10 ng/mL) than at midtrimester (median 20.07 ng/mL) and reached a peak in term labor (median 258.80 ng/mL). The AF/MS ratio varied from a median of 4.34 at midtrimester and 33.7 at term labor. The MS/CS ratio was 0.4. Migration inhibitory factor immunoreactivity was found in different cell layers of the extraembryonic membranes.
Conclusions: The increased secretion of MIF in AF at term, particularly at term labor, suggests that MIF contributes to the inflammatory events leading to labor.