Objective: To evaluate the transplacental passage of vancomycin in term, uninfected pregnant women.
Methods: A single vancomycin 1-g dose was administered intravenously at four separate time intervals to 13 uncomplicated nonlaboring women undergoing scheduled cesarean delivery. Samples of maternal blood and fetal cord blood were collected at time of delivery and vancomycin concentrations assayed.
Results: Vancomycin concentrations in maternal serum ranged from 2.6 to 19.8 mcg/mL. In cord blood samples, vancomycin concentrations ranged from 2.8 to 9.4 mcg/mL and persisted above the group B streptococci vancomycin breakpoint of 1 mcg/mL. Only 6 of 13 women received the full 1-g vancomycin dose because 53.8% (7 of 13) had some manifestation of red man syndrome during the infusion. No other short term sequelae were identified in any patients or their fetuses. A strong correlation (r(2)=0.93, P<.001) between cord and maternal serum concentrations versus time was noted. Cord vancomycin concentrations approached maternal serum concentrations 4 hours after the infusion ended.
Conclusion: Vancomycin crosses the placenta in a predictable manner in concentrations that exceed the usual group B streptococci breakpoint. Adverse events were common, suggesting that longer infusion times and weight adjusted doses should be used.