Effect of laser coagulation on placental vessels: histological aspects.

In order to evaluate the effect of laser coagulation on placental vessels and to define the optimal power density that should be used for this procedure, coagulation of placental vessels and histological examination were performed on freshly delivered placentae. This study suggests that 45- to 55-watt (6,000-7,666 J/cm2) shots can cause adequate placental injury. The extent of vascular lesions depends upon incident beam energy, fiber diameter, distance and angle to the vessel.