Placental endothelial nitric oxide synthase in multiple and single dose betamethasone exposed pregnancies.

Objective: To compare endothelial nitric oxide synthase expression and capillary density (CDS) in placentas exposed to single or multiple courses of betamethasone.

Study Design: Placental specimens exposed to single vs repeat courses of betamethasone were analyzed through immunohistochemistry and digital image quantification for endothelial nitric oxide synthase and CD34. Quantified endothelial nitric oxide synthase staining, calculated capillary density, ratio of endothelial nitric oxide synthase to capillary density, and clinical characteristics were compared. Linear regression was performed with these as dependent variables.

Results: Mean and maximum capillary density were increased (P = .013 and .005) and the ratio of endothelial nitric oxide synthase to capillary density decreased (P = .016) in specimens exposed to 4 courses of betamethasone compared with 1 to 3 courses. Exposure to 4 courses of betamethasone was associated with increased capillary density, but not with endothelial nitric oxide synthase expression.

Conclusion: Exposure to 4 courses of betamethasone is associated with increased placental capillary density. The placental effects of multiple courses of betamethasone are unrelated to endothelial nitric oxide synthase expression.