Nexplanon might increase the chance of developing a serious blood clot, according to Nexplanon’s label. This may especially apply to those with other risk factors, like smoking. Blood clots can lead to potentially fatal events, such as stroke, heart attack, pulmonary embolism, or deep vein thrombosis. Nexplanon’s label recommends telling healthcare providers at least four weeks before having surgery or being on bed rest, as bed rest and surgery can increase the chances of developing blood clots. A 2012 study linked the usage of birth control implants that go under the skin with a 40 percent higher risk of the development of venous blood clots.