Progestin only birth control pills are birth control pills containing only the synthetic hormone of progesterone which a woman’s body produces naturally. Often it is called the “mini-pill” or “POP” as it only contains one hormone instead of two which regular birth control pills have. Regular birth control contains both the synthetic progesterone as well as estrogen which a woman’s body also produces. 

Progestin only pills may not have as many side effects as regular birth control pills due to no having the estrogen in them. The synthetic progesterone hormone makes a woman’s body “think” that is pregnant and therefore stops a woman’s body from ovulating. Progestin only birth control also causes changes within a woman’s uterus and makes a woman less likely to become pregnant if an egg is released. It also thickens the mucus between the vagina and uterus which sperm released into the vagina will have to penetrate in order to become pregnant. This additional mucus helps prevent the sperm from actually entering the uterus.