Fibrin and platelets in menstrual discharge before and after the insertion of an intrauterine contraceptive device.

Eighteen samples of menstrual blood, taken before and after the insertion of an intrauterine contraceptive device (IUD), were collected from the uterine cavity during the first 32 hours of menstruation and studied with light and electron microscopy for the presence of fibrin and platelets. In 12 of the 18 samples extravascular fibrin and platelet aggregates with a high degree of transformation were found. Intravascular thrombi were seen in pieces of tissue in two preinsertion samples. The absence of any intravascular platelets or fibrin was the only consistent difference in postinsertion samples compared to preinsertion samples. This study demonstrates that, contrary to the current belief, clot formation and platelet aggregation do occur in menstrual blood. This process is uninfluenced by the presence of an IUD.