Gannett Health Services
Ho Plaza
Cornell University
Ithaca, NY 14853-3101
Tel: 607 255-5155
Email: gannett@cornell.edu
Minipills are progesterone-only birth control pills (i.e. they contain no estrogen). The progesterone affects the mucus around the cervix and makes it harder for the sperm to enter the uterus. It also affects the transport of the egg through the fallopian tubes to prevent fertilization and can inhibit ovulation in some people. Minipills are more than 95% effective, slightly less than regular birth control pills.
Learn more by reading our Fact Sheet (pdf) on this topic.