Oral contraceptives for the prevention of osteoporosis.

Oral contraceptives are a safe and acceptable form of contraception in perimenopausal women and may be effective in maintaining bone mass prior to menopause. Studies of the bone-sparing properties of oral contraceptives are difficult to interpret because of confounding variables, such as age, smoking, duration of use, exercise, menstrual function and endocrine diseases. Nevertheless, the results of many studies suggest that premenopausal use of oral contraceptives is associated with higher bone density than is nonuse. Long-term premenopausal oral contraceptive use allows women to enter menopause with bone density that is 2-3% higher than in nonusers. The optimal duration of use and dosage of estrogen and the clinical importance of this effect remain to be determined.