This study investigates the use of forward scattered light (FSL) measurements for early blood clot detection in extracorporeal membrane oxygenators, a method potentially superior to the current standard of monitoring pressure differences (ΔP) which fails to detect smaller, early-stage clots. Despite several modifications, FSL measurements were unable to reliably detect clots in an in vitro test circuit, whereas the current clinical gold standard of pressure measurements successfully detected fulminant clot formation in multiple experiments.