There are many herbs/plants in nature that can effect a woman's hormone levels to the point where it can make conception difficult or make the womb inhospitable for the fertilized egg to attach and grow, but I am not convinced they are any safer than the chemical birth control pills. Hormones are a risky thing to mess around with and should not be a do it yourself project for anyone. Women have been trying to come up with plant formulas for hundreds of years that will either prevent conception or act as an aborticant, nothing is foolproof. Since hormone imbalances are often associated with cancers, along with poor diet and toxic bodies, I would be very hesitant to self treat with plant hormones.