ObjectiveTo determine which of four types of catheters would be the least likely to become displaced spontaneously when employed as a fetoamniotic shunt, by testing the force required to remove the catheters from a lamb's bladder.MethodsThe catheter designs tested were unfeathered straight, unfeathered pig-tailed, superficially feathered, and deeply feathered. The catheters were placed percutaneously into the urinary bladders of recently euthanized newborn lambs. The force required to withdraw the catheters was determined, employing nine measurements for each catheter design.ResultsThe mean force required to remove the straight catheter was 12 g (95% confidence interval [CI] 2–21 g), the pig-tailed catheter 22 g (95% CI 13–32 g), and the superficially feathered catheter 149 g (95% CI 139–160 g). Extracting the deeply feathered catheter consistently required a force greater than 300 g, which was the upper limit of detection for our instruments.conclusionFeathering the catheter increases the force required to extract it from a fetal viscus. We believe that use of feathered catheters will significantly reduce the incidence of unwanted spontaneous displacement.