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Updated: Oct 16, 2025

Guide Wire Assisted Catheterization and Colored Dye Injection for Vascular Mapping of Monochorionic Twin Placentas
Published on: September 5, 2011
Enhanced elimination of betamethasone in dichorionic twin pregnancies
Grazielle de Fátima Pinto Rodrigues1, Jhohann Richard de Lima Benzi2, Luísa Helena de Castro Matos1
1Department of Gynecology and Obstetrics, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil.
Aim:
No study has evaluated the betamethasone pharmacokinetics in twin pregnancies according to chorionicity. This study aimed to describe and compare the betamethasone pharmacokinetic parameters in singleton and dichorionic (DC) and monochorionic twin pregnancies in the third trimester of pregnancy.
Methods:
Twenty-six pregnant women received 2 intramuscular doses of 6 mg of betamethasone sodium phosphate plus 6 mg betamethasone acetate due to preterm labour. Serial blood samples were collected for 24 hours after the first intramuscular dose of betamethasone esters. Betamethasone plasma concentrations were quantified using a validated liquid chromatography-tandem mass spectrometry analytical method, and the pharmacokinetic parameters were obtained employing a noncompartmental model. Preliminary data on the betamethasone placental transfer are also presented.
Results:
The geometric mean (95% confidence interval) of AUC0-∞ 645.1 (504.3-825.2) vs. 409.8 (311.2-539.6) ng.h/mL and CL/F 17.70 (13.84-22.65) vs. 27.87 (21.17-36.69) were significantly different, respectively, in singleton pregnancies when compared to DC twins.
Conclusion:
Data from this study suggest that the presence of 2 foetoplacental units may increase the betamethasone metabolism by hepatic CYP3A4 and/or placental 11β-HSD2 enzymes. Pharmacokinetic-pharmacodynamic clinical studies are needed to investigate whether these betamethasone pharmacokinetic changes have clinical repercussions for the newborns and require dose adjustment in DC twin pregnancies.
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