Modulation of lipopolysaccharide-induced chorioamnionitis in fetal sheep by maternal betamethasone.

OBJECTIVE: We tested the hypothesis that the order of exposure to maternal betamethasone and intra-amniotic (IA) lipopolysaccharide (LPS) will differentially modulate inflammation in the chorioamnion. STUDY DESIGN: Time-mated Merino ewes with singleton fetuses received saline alone, IA LPS alone, maternal betamethasone before LPS, or betamethasone after LPS. We assessed inflammatory markers in the chorioamnion and the amniotic fluid. RESULTS: Inflammatory cell infiltration, expression of myeloperoxidase, serum amyloid A3 (acute phase reactant) in the chorioamnion, and levels of interleukin (IL)-8 in the amniotic fluid increased 7 days after LPS exposure. Betamethasone prior to LPS decreased infiltration of the inflammatory cells, CD3+ T cells, and decreased the levels of IL-1β and IL-8 in the amniotic fluid. CONCLUSIONS: Betamethasone 7 days prior to LPS exposure suppressed LPS-induced inflammation. The markers of inflammation largely had returned to the baseline 14 days after LPS exposure.