Ectopic pregnancy may occur (rarely). May increase risk of thromboembolism. Use with caution in renal impairment. Etonogestrel serum levels and contraceptive efficacy may be significantly decreased by potent hepatic enzyme inducer (use not recommended in women chronically taking hepatic enzyme inducers). Use with caution in overweight women. Not for use prior to menarche. Improper insertion may lead to unintended pregnancy or may cause difficult or impossible removal, and menstrual bleeding patterns are likely to be altered. Does not protect against HIV infection or other sexually-transmitted diseases. Use associated with a slight increase in frequency of breast cancer (studies not consistent). Use with caution in risk factors for coronary artery disease (may lead to increased risk of MI). May have a dose-related risk of vascular disease and hypertension. Use with caution in depression. Use with caution in diseases which may be exacerbated by fluid retention, including asthma, epilepsy, migraine, diabetes or renal dysfunction. May have a dose-related risk of gallbladder disease. May cause glucose intolerance. May affect serum triglyceride and lipoprotein levels (increased HDL-C, decreased LDL-C, and increased triglycerides; use with caution in familial lipoprotein metabolism defects). Use with caution in history of migraine. Estrogens may cause retinal vascular thrombosis (rarely). Risk of cardiovascular side-effects increases in women who smoke cigarettes, especially those over 35 years of age. Whenever possible, therapy should be discontinued at least 4 weeks prior to and for 2 weeks following elective surgery associated with increased risk of thromboembolism or during periods of prolonged immobilization.