Progestin-Only Pill Patient Information Fact Sheet

What is the progestin-only pill?
As its name implies, the progestin-only pill (POP) contains only progestin. It is an alternative to combined hormonal contraceptives (pill, patch or vaginal ring), which contain both estrogen and a progestin. The POP is used for women in whom it is preferable to avoid estrogen. It is not as effective as combined hormonal contraceptives and so is normally prescribed only when there is a reason why the woman is unable to take one of these. The POP is between 90% and 99% effective as a method of contraception.

How does it work?
In some women, the POP completely suppresses ovulation. In others, ovulation may occur each month or only in some months. The progestin causes the lining of the womb (the endometrium) to become thinner, which decreases the likelihood of a fertilized egg implanting. In addition, the cervical mucus becomes thicker and therefore more resistant to sperm. The motility within the fallopian tubes is also affected so that eggs will have difficulty in passing down the tubes.

What are the advantages of the progestin-only pill?

  • It can be taken by women who are breastfeeding.
  • It can be taken at any age (but is often given to women over 35 who smoke or those who cannot take a combined hormonal contraceptive for other reasons).
  • It does not raise blood pressure.
  • It can help to relieve premenstrual symptoms and often makes periods less painful.
  • It is a totally reversible form of contraception.
What are the disadvantages of the progestin-only pill?
  • Some research suggests that the POP may be less effective in women weighing more than 150 pounds.
  • It must be taken at a regular time each day to maintain optimum effect. If it is taken late or if a pill is missed altogether, the contraceptive effect drops markedly. A pill is said to be "missed" if taken 3 hours later than usual.
  • Some women may experience irregular bleeding or breakthrough bleeding (bleeding between periods).
  • As with combined hormonal contraceptives, the POP offers no protection against sexually transmitted diseases, including HIV.

What are the risks of taking the progestogen-only pill? 
If fertilization does occur, there is a small risk that the resultant pregnancy may be ectopic. An ectopic pregnancy is one that develops outside the womb, usually in a fallopian tube. Ectopic pregnancies are rare but can be dangerous. If a period is late and sudden pain develops, seek medical attention immediately. The incidence of ectopic pregnancy in women taking a POP is still much lower than in women who were not taking any contraception when they conceived.

A small number of women may develop cysts on the ovaries while taking the POP. These are harmless and will disappear without treatment. In some women cysts will cause pain while in others cysts will not cause any problems.

It is thought that the risk of developing breast cancer in women taking a POP is similar to that in women taking a combined hormonal contraceptive. However, the evidence of a link between breast cancer and the POP is based on a much smaller user population than that for combined hormonal contraceptives and is, therefore, less conclusive.

What are the different types of progestin-only pill?
The POP is taken every day without a break. The new pack is started the day after the previous pack is finished. A period may still occur as usual but in some women periods may stop altogether. Different tablets contain different levels of progestin and the doctor prescribing will make a choice about which is the most suitable. POPs that may be prescribed include norethinedrone (Micronor, Nora BE, Nor QD, Jolivette, Errin, Camila).

Further information
Centers for Disease Control and Prevention: www.cdc.gov/reproductivehealth/UnintendedPregnancy/Contraception.htm
Association of Reproductive Health Professionals: www.arhp.org/Publications-and-Resources/Quick-Reference-Guide-for-Clinicians/choosing/Progestin-Only-OCs

Last Reviewed: May 2013