Birth control pills are a type of contraception in the form of small tablets that is swallowed each day. Most pills contain two type of synthetic (man-made) female hormones, progestin and estrogen, and are called the "combination oral contraceptive". The hormones estrogen and progesterone are normally produced by the ovaries.
There are many different types of the combination oral contraceptives. The estrogen and progestin prevent pregnancy by suppressing the pituitary gland, which stops the development and release of the egg in the ovary, called ovulation. The progestin also helps to prevent the sperm from reaching the egg and changes the lining of the uterus.
One type of pill contains only one hormone, progestin, and is called either the "progestin-only pill," or the "mini-Pill." It works by suppressing ovulation and helping to prevent the male's sperm from reaching the egg. This pill makes it difficult for the sperm to enter the womb by thickening the mucus at the entrance of the womb. It also cause changes in the endometrium (lining of the uterus) that makes implantation difficult