A multiphasic method of contraception that provides for sequentiallyadministering to a femal of child bearing age: (a) a Phase I compositioncontaining a progestogen in an amount equivalent to about 0.5 to about 1.5mgnorethindrone acetate and an estrogen in an amount equivalent to about 5 toabout 30 mcg of ethinyl estradiol for about 4 to about 7 days； (b) a Phase IIcomposition containing a progestogen in an amount equivalent to about 0.5 toabout 1.5mg of norethindrone acetate and an estroben in an amount equivalentto about 10 to about 40 mcg of ethinyl estradiol for about 8 to about 16 days；(c) a Phase III compositions containing a progestogen in an amount equivalentto about 0.5 to about 1.5 mg of norethindrone acetate and an estrogen in anamount equivalent to about 5 to about 30 mcg of ethinyl estradiol for about 4to about 7 days； and (d) optionally, a Phase IV composition which is a placeboor a non-steroidal component, such as for example, ferrous fumarate, for about2 to about 9 days, wherein the ethinyl estradiol equivalent amount of estrogenin the Phase II composition is at least 5 mcg greater than the ethinylestradiol equivalent amount of estrogen in each of the Phase I and IIIcompositions. Preferably the sequential administration of the Phase I, II andIII compositions is repeated the day following the completion of theadministration of the Phase III compositions to provide an extended cyclemultiphasic oral contraceptive method.
