Low-dose oral contraceptives and bone mineral density: an evidence-based analysis.

We reviewed studies of the association of oral contraceptive (OC) use and bone mineral density (BMD). We limited the review to studies of women using low-dose oral contraceptives and that measured BMD by bone densitometry. A total of 13 studies met the inclusion criteria. Nine of these showed a positive effect of OC use on BMD, and four did not show an association. However, none of the studies showed a decrease in BMD with OC use. We classified the level of evidence from each study according to the guidelines of the US Preventive Services Task Force. The level of evidence supporting a positive association between OC use and increased BMD is II-1. There is fair evidence (Category B) to support the position that OC use has a favorable effect on BMD. We made suggestions for a study design that could yield Level I evidence.