What is the major cardiovascular risk of combining tobacco use with estrogen-containing oral contraceptives?

Estrogen-containing combined oral contraceptives (COCs) increase the risk of venous thromboembolism (VTE), stroke, and myocardial infarction through their procoagulant effects. Tobacco smoking independently increases cardiovascular risk through nicotine-mediated vasoconstriction, platelet aggregation, and atherosclerosis. The combination of smoking and COCs is synergistic and dramatically increases the risk of arterial thrombosis, particularly in women over 35 who smoke more than 15 cigarettes per day. This combination is generally contraindicated. Dentists should be aware of this risk when reviewing medications and counseling patients.