COMPARISON BETWEEN ORAL AND INTRAMUSCULAR DEXAMETHASONE IN SUPPRESSING UNCONJUGATED ESTRIOL LEVELS DURING THE 3RD-TRIMESTER

OBJECTIVES: Unconjugated estriol production depends on fetal adrenal a ndrogen precursors. Fetal exposure to exogenous glucocorticoids result s in adrenal suppression with a subsequent decrease in maternal serum unconjugated estriol levels. We compared the efficacy between oral and intramuscular dexamethasone in maternal serum unconjugated estriol su ppression at 48 hours after the initial dose among women at risk for p reterm delivery. STUDY DESIGN: Twenty-four gravidas at risk for preter m delivery were randomized to receive either 6 mg intramuscular or 8 m g oral dexamethasone every 12 hours for a total of 4 doses. Blood samp les (9 mt) were obtained before the initial dexamethasone administrati on and again after the fourth dose. Serum was separated and frozen at -70 degrees C and subsequently underwent batch analysis. Unconjugated estriol levels were determined by radioimmunoassay with intra-assay an d interassay coefficients of variation of 7.9% and 5.5%, respectively. All values are reported as mean +/- SD. The primary statistical analy sis was a t test, with P < .05 considered significant. RESULTS: At the time of dexamethasone administration, gestational ages in both groups were similar. Predexamethasone and postdexamethasone unconjugated est riol levels were also similar between the intramuscular and oral group s (5.39 +/- 3.99 vs 1.80 +/- 2.49 ng/mL and 6.05 +/- 3.00 vs 1.61 +/- 1.03 ng/mL, respectively, P > .05). No difference in percent decrease in unconjugated estriol levels was found between the intramuscular (0. 67 +/- 0.24) and oral (0.65 +/- 0.39) groups. CONCLUSION: Oral dexamet hasone (8 mg) produces similar maternal serum unconjugated estriol sup pression compared with intramuscular dexamethasone (6 mg) when evaluat ed 48 hours after administration.