The birth control pill has the active ingredients as progesterone and the estrogen. The biphasic birth control pill is a type of a combination pills, these combination pills contains the mixtures of the two ingredients in various proportions. In biphasic birth control pill the amount of estrogen remains the same what varies is the amount of progesterone.

The amount of progesterone is increased gradually during the cycle. During the menstrual cycle level of hormones in the body are subjected to change once by these biphasic birth control pills. The estrogen level remains the same for each day while the progestin levels are increased at the half way into the cycle. The estrogen level is uniform but the ratio of the progestin to the estrogen is gradually increased to thicken endometrium which won’t allow the egg to travel to the uterus via the fallopian tubes hence preventing any pregnancy risk. The progestin to estrogen ratio is increased further during the second half of the menstrual cycle.

This is done to help the process where lining of the uterus shedding normally occurs. These pills are continued for initial weeks then for the remaining seven days there are placebo pills which does not contain any hormone. Some of the biphasic birth control pills are Jenest, Necon 10/11, Nelova 10/11, Mircette and Ortho-Novum 10/11.