Contraception: the mini (progestogen-only) pill
What is the mini pill?
The mini pill or progestogen-only pill (POP) is an alternative oral contraceptive to the combined pill. It contains a low dose of progestogen, but does not contain any oestrogen. Brands available in Australia include Microlut, Locilan 28 Day, Micronor, and Noriday 28.
How does the mini pill work?
The mini pill contains synthetic progestogens which mimic the natural hormone, progesterone, which is produced by your body every month mostly in the last 2 weeks of your menstrual cycle.
Progestogens thicken the cervical mucus and make the lining of the womb thinner. The thicker cervical mucus makes it very difficult for the sperm to get through the entrance of the uterus (womb) to fertilise the egg and the thin lining of the womb makes it very difficult for an egg to implant even if it does become fertilised. Progestogens can also inhibit the release of the egg from the ovary in some, but not all, menstrual cycles.
Effectiveness at preventing pregnancy
The effectiveness of a contraceptive method can be measured for perfect use and typical use.
- Perfect use is when instructions are followed precisely. The failure rate for perfect use of the mini pill is about one per cent. So if used perfectly, about one women in every 100 will become pregnant in a year.
- Typical use is what tends to happen in reality. Typical use failures include failures due to incorrect use. The failure rate for the mini pill is about 8-9 per cent in a year of typical use. The mini pill tends to be less effective in younger, more fertile women than in older women.
Some of the advantages of the mini pill are that it:
- may be suitable for women who cannot take the combined pill because of the oestrogen it contains (for example, those with heart disease, high blood pressure, a history of stroke, those at risk of blood clots, and women who experience certain types of migraine headaches);
- can be used if you are breast feeding;
- doesn’t interfere with sexual spontaneity; and
- allows fertility to return without delay after you stop taking it.
Some of the disadvantages of the mini pill are that it:
- must be taken at the same time every day;
- is less effective than the combined pill;
- can only be obtained on prescription;
- may result in spotting or irregular bleeding;
- does not protect against sexually transmitted diseases;
- is not recommended for women with certain medical conditions (including severe liver disease, a history of breast cancer, malabsorption disorders, or those who have had a previous ectopic pregnancy); and
- may not be suitable for women taking certain medicines (such as anti-epileptic medicines, St John’s wort or certain antibiotics).
How is it used?
The mini pill is taken continuously on a daily basis, at the same time each day.
If you forget to take a pill within 3 hours of the usual time you take it, take the missed pill as soon as possible. Take the next pill at the usual time, even if that means taking 2 pills in one day. Alternative contraception should be used until 3 pills have been taken at the usual time.
If you have vomiting or diarrhoea, you may not absorb the mini pill, and you should use a barrier method of contraception, such as a diaphragm or condom for the next 2 to 14 days. Your doctor will be able to advise you.
Common side effects associated with use of the mini pill may include:
- irregular menstrual bleeding;
- breast tenderness;
- possible mood changes;
- decreased libido; and
- 1. Progestin-only oral contraception (revised June 2009). In: eTG complete. Melbourne: Therapeutic Guidelines Limited; 2013 Jul. http://online.tg.org.au/complete/ (accessed Aug 2013).
2. Family Planning NSW. Progestogen-only pill (mini pill) (updated May 2013). http://www.fpnsw.org.au/936515_8.html (accessed Aug 2013).
3. Family Planning Victoria. The mini pill (updated Jan 2010). http://www.fpv.org.au/sexual-health-info/contraception/pills/mini-pill/ (accessed Aug 2013).
4. MayoClinic.com. Minipill (progestin-only birth control pill) (updated 1 Dec 2011). http://www.mayoclinic.com/health/minipill/MY00991 (accessed Aug 2013).