How does depo-estradiol work as a contraceptive?

It is not ideal: D-estradiol like the birth control pill suppresses the release of hormones that stimulate the ovary. This results in lack of ovulation. The problem is that it overstimulates the uterine lining. Progesterone is needed to prevent possible pre-cancerous changes in the uterus from the estradiol. Most contraceptives have both Estradiol and progesterone. Some have just progesterone.