(212) Comparison of transplacental transfer of clarithromycin in singleton and twin pregnancy

Objective: Ureaplasma is one of the most commonly identified pathogens in the presence of amniotic fluid infection. Previous studies have reported that clarithromycin was the most effective macrolide which reached minimal inhibitory concentrations capable of inhibiting Ureaplasma. The aim of this study was to evaluate the difference of transplacental transfer of clarithromycin in singleton and twin pregnancy.

Study Design: Singleton and twin pregnant women with preterm premature rupture of membrane were prospectively enrolled and received 500 mg of oral clarithromycin twice daily until delivery. At the time of delivery, maternal and cord blood were obtained simultaneously. Clarithromycin concentration was measured using liquid chromatography-tandem mass spectrometry. The percentage was calculated between clarithromycin level of the cord and the maternal serum.

Results: A total of 35 pregnant women (21 singletons, 14 twins) and 46 fetuses (21 singletons, 25 twins) were enrolled. The median cord to maternal clarithromycin concentration percentage (C-M percentage) was 6.38% in singletons and 5.38% in twins (p=0.228) (Table 1). In between twins, there was no significant difference in C-M percentage (p=0.867). In twins who had larger birthweight, the C-M percentage was 5.15% (4.36-11.24%), and in their co-twins who had smaller birthweight, the C-M percentage was 6.95% (4.01-11.11%) (p=0.639) (Table 2).

Conclusion: There was no difference in placental transfer of clarithromycin between singleton and twin pregnancy. On the base of this study, dosage adjustment is not required in twin pregnancy.