Birth control pills are a form of oral contraceptive that consist of small amounts of hormones. They work to keep eggs from being released from the ovary, thus preventing pregnancy. Some types bring temporary changes to the uterus’s lining, which makes it less likely for a fertilized egg to implant. Birth control pills are typically available in a pack with many pills. They should be taken orally on a daily basis to achieve the desired effect. 
Birth control pills that contain both progesterone and estrogen may work to prevent pregnancy in two ways:
– They prevent ovulation, meaning the ovaries will not release an egg every month
– They may cause cervical mucus in the body to become thicker. This is the fluid around the cervix that helps with the transport of sperm to the uterus for egg fertilization. Thickened mucus may prevent sperms from reaching your uterus.
Birth control pills that only contain progestin may have a different mechanism. They can think of the endometrium and thicken the cervical mucus. The endometrium is the uterus’s lining, where egg implantation occurs. The thinner lining makes it more difficult for egg implantation to occur and thus prevents pregnancy.