Saw palmetto extract may decrease the effectiveness of estrogen products by reducing estrogen levels in the body via its antiestrogenic effects.  It can interfere with the use of birth control pills that contain estrogen as an active ingredient. As a result, it is recommended that an additional form of birth control, such as a condom, be used to prevent pregnancy in patients taking birth control pills with saw palmetto extract. In addition, saw palmetto extract can also interfere with hormone replacement therapy by reducing the effectiveness of estrogen pills. The combination of saw palmetto extract with estrogen products should be used with caution.