EDIT: I have learned the name of the method! It is called Centchroman.
Centchroman has been available in India since around 1990, and is marketed there under the brand names CentronĀ® and SaheliĀ®. Most women I know have never heard of it. As far as I know, it works by causing ovulation to occur asynchronously with the development of the uterine lining, thus impeding implantation.
If you have information about Centchroman, know of related resources, or have tried Centchroman yourself, I would really appreciate hearing from you. My body does not tolerate hormonal birth control, so I want to explore other methods. Thank you!
Thanks to
mmmmhmmm for the link to this
Centchroman bulletin board. Click on the second topic,
Centchroman FAQ for a basic overview.