How do different kinds of birth control pills work?
Combination birth control pills suppress ovulation — keeping your ovaries from releasing an egg. Combination birth control pills also thicken cervical mucus and thin the lining of the uterus (endometrium) to keep sperm from reaching the egg. The minipill thickens cervical mucus and thins the endometrium — preventing sperm from reaching the egg. The minipill also sometimes suppresses ovulation. Unlike combination birth control pills, the minipill doesn’t contain estrogen. The progestin dose in a minipill is also lower than the progestin dose in any combination oral contraceptive pill.
