Contraceptive methods and formulations for use therein

A method for preventing conception in a mammal, comprising:

• administering an amount of a gonadotropin hormone releasing hormone composition effective to maintain serum levels of said gonadotropin hormone releasing hormone composition at a level effective to inhibit ovulation for a first period of time comprising about two months to about six months;
• simultaneously administering an amount of an estrogenic hormone effective to maintain serum levels of said estogenic hormone at a level equivalent to a serum level of estradiol of from about 25 to about 140 pg/ml for said first period of time;
• and
• administering an amount of a progestogen effective to maintain serum levels of said progestogen at a level equivalent to a serum level of progesterone of from about 5 to about 20 ng/ml for a second period of time comprising about 5 to about 20 days, said second period of time running simultaneously with a portion of said first period of time;