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Progestogen Only Pill

Sometimes Called the 'Mini-Pill'

As these pills contain only one hormone, progestogen, they may be used by women who cannot tolerate or should not take oestrogen for medical reasons.

How does the Progestogen Only Pill work?

The Progestogen Only Pill (POP) prevents pregnancy by:

  • Changing the mucus in the cervix - the mucus in the cervix thickens so that sperm cannot penetrate into the uterus and fallopian tubes to fertilise the egg. The mucus changes occur in all women taking the POP. These changes are effective 48 hours after beginning the pill.
  • Altering the endometrium - the endometrium (lining of the uterus) changes, making it unsuitable for the egg to implant.
  • Interfering with the process of ovulation - this happens in up to 60% of women taking the POP and is most common in older women and those who are breastfeeding. Interfering with the process of ovulation takes 7 days of regular pill taking to take effect. These women are more likely to notice irregular or absent periods while on the POP.

How effective is the POP?

The POP is 97-99% effective when taken correctly. Effectiveness depends on how regularly you take your pill and on your age. Women over 40 and those who are breastfeeding have the lowest rate of pregnancy.

Some studies suggest that women weighing over 70 kilograms need to double the dose of the POP, depending on their age.* This should be discussed with a medical practitioner.

How do I take the POP?

The pills are taken on a continuous daily basis with no breaks and no inactive (sugar) pills.

You can start at any time during the menstrual cycle. If taken on the first day of the period the POP is effective immediately. If started at any other time during the menstrual cycle, the mucus effect will provide protection after 48 hours. You may want to wait a full 7 days to benefit from the potential effect on ovulation.

The most important thing is that the pill be taken regularly and at the same time every day.

If you are more than 3 hours late in taking the POP the risk of pregnancy increases. The levels of progestogen in your body are at their lowest at around the time you take your pill. Some people therefore suggest that your regular pill taking time should be at a time of day other than when you usually have intercourse.

What if I miss pills?

If you are more than 3 hours past your regular pill taking time, take it as soon as you remember and then resume taking your pills at the regular time.

If you vomit within 2 hours of taking the pill it may not be effective - take another pill as soon as you can. Severe diarrhoea can sometimes interfere with the effectiveness of the POP.

You will need to take the POP for 48 hours to regain the effect on the mucus and 7 consecutive days to regain the effect on ovulation.

Emergency contraception (EC) is available over the counter at pharmacies if you have unprotected sex before you regain your contraceptive cover. The sooner EC is taken after unprotected sex the more effective it is at preventing pregnancy, and its effectiveness is significantly increased when taken within 24 hours. It can be taken up to 120 hours (5 days) after intercourse, however, effectiveness decreases as time passes.

Advantages

The POP:

  • is a very effective form of contraception
  • has no serious side effects
  • can be used by women who cannot tolerate oestrogen
  • does not increase the risk of deep vein thrombosis
  • allows fertility to return quickly after stopping
  • is safe to use while breastfeeding
  • is not affected by taking most commonly-prescribed antibiotics
  • has no effect on migraine headaches
  • is safe for women who smoke
  • may be a healthier choice for women over 40 years.

Disadvantages

The POP:

  • needs to be taken at a regular time to be effective
  • may alter menstrual patterns
  • may increase the chance of developing ovarian cysts if there has been a past history of this problem.

Is there anything else I need to know?

The POP may be unsuitable for women who:

  • have heart disease
  • have active liver disease
  • take certain prescribed medication such as anti-epileptic drugs
  • have undiagnosed vaginal bleeding.

*Guillebaud, John. (2004) Contraception: your questions answered. 4th ed. London, UK: Churchill Livingstone. pp 290.

Practising safe sex reduces the risk of contracting HIV and other sexually transmissible infections (STIs).

Page last updated Thu, 15 May 2008 15:49