Contraception: the combined pill

What is the combined pill?

The combined oral contraceptive pill (often referred to simply as ‘the pill’) contains synthetically produced oestrogen and progestogen. These synthetic hormones imitate the natural hormones produced by women’s ovaries.

How does the pill work?

The pill works mainly by preventing the release of of an egg from the ovaries each month. The pill also thickens cervical mucus to form a barrier to sperm, so that they can’t enter the uterus and fallopian tubes.

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 combined pill is 0.3 per cent. So, when used perfectly, less than one woman 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 combined pill is about 8-9 per cent in the first year of typical use.

Advantages

  • The pill is extremely effective and reliable when taken as directed.
  • It may result in periods becoming shorter, lighter, less painful and more regular.
  • The combined pill can be used to manipulate the menstrual cycle (e.g. the pill can be used to skip periods for convenience or for certain events, such as holidays).
  • Fertility is not permanently affected, and usually returns soon after stopping the pill.
  • The pill can be used to improve acne.
  • It may help improve premenstrual syndrome.
  • The pill can reduce the risk of ovarian cysts and can help manage the symptoms of polycystic ovary syndrome.
  • Women taking the pill have a reduced risk of ovarian cancer and endometrial cancer (cancer of the lining of the uterus).

Disadvantages

  • The pill is only available on prescription.
  • Some formulations can be expensive.
  • The pill does not protect against sexually transmitted diseases.
  • For the pill to be effective, you need to remember to take it daily.
  • It cannot be used by women who have had breast cancer, stroke, heart attack, deep vein thrombosis (a blood clot in the deep veins of the body), certain types of migraine headaches, heart disease, liver disease and smokers aged over 35 years.
  • The risks of the pill may outweigh the benefits in women with high blood pressure, diabetes, high cholesterol, unexplained vaginal bleeding, and those taking certain medicines (e.g. anti-epileptics or St John’s wort).
  • The pill should generally not be used during breast feeding, as the oestrogen can suppress lactation.

How is it used?

The combined pill usually comes in a packet containing 28 pills. Each packet contains between 21 and 26 active (hormone) pills, and between 2 and 7 sugar pills (pills without any hormones).

Combined oral contraceptives are either:

  • monophasic (where each active pill has the same dose of progestogen and oestrogen); or
  • multiphasic (where active pills have different doses of progestogen and/or oestrogen).

Your doctor can advise you as to the most appropriate type of pill for you and how to take it.

Taking the pill

You should start taking the pill on the first day of your period, carefully following the instructions that come with the packaging.

You should take one pill daily, at about the same time every day until you have finished the packet. You will usually have vaginal bleeding when taking the sugar pills. The day after you finish one packet, you should start the next packet of pills.

When starting most types of pill for the first time, you should not rely on the effectiveness of the pill alone for the first 7 days, so use another form of contraception (such as a condom) as well during this time.

It is possible for women to take the active hormone pills continuously for 3 to 12 months, to avoid bleeding. To do this, you simply skip the sugar pills and take a hormone pill every day. This can be especially useful for women who have headaches during the hormone-free period, suffer from premenstrual syndrome, or have heavy or painful periods. It is best to seek advice from your doctor if you are planning on doing this.

What to do if you miss a pill

If you miss a pill, you should check the instructions on the packet for what to do. It’s also a good idea to check with your healthcare provider for advice on what to do if you miss a pill.

The following general information applies to most, but not all, types of combined pill.

Less than 24 hours late

If you are less than 24 hours late taking a pill, take it as soon as possible and take the next pill at the usual time. You will still be protected against pregnancy.

More than 24 hours late

If you are more than 24 hours late taking a pill, take the missed pill as soon as possible and take the next pill at the usual time (even if that means taking 2 pills at once). Keep taking your pill daily after this. You will also need to use an additional form of contraception (such as condoms) for the next 7 days to ensure you are protected against pregnancy.

If there are fewer than 7 hormone pills left in your packet, follow the instructions above but in addition, once you have finished the remaining hormone tablets in the packet, you should skip the sugar pills and go straight to taking the hormone pills in the next packet.

Taking the pill when you are sick

If you have vomiting or diarrhoea, you may not absorb the pill. You should use an alternative method of contraception, such as a diaphragm or condom, for the next 7 days – follow the information on missed pills. Your doctor will be able to advise you.

Some antibiotics and other medicines can also interfere with the absorption of the pill – check with your doctor.

The pill should also be discontinued for 4-6 weeks before any major surgery associated with an increased risk of blood clotting. Talk to your doctor, who will advise you on whether you need to stop taking the pill and alternative methods of contraception.

Side effects

The combined pill can cause the following side effects:

  • breast tenderness;
  • irregular vaginal bleeding; and
  • nausea.

These side effects usually resolve after about 3 months of taking the pill.

Less common side effects include:

  • fluid retention and bloating;
  • headaches;
  • reduced libido;
  • irritability; and
  • irregular skin pigmentation on the face (particularly if exposed to the sun).

In rare instances, the combined pill can cause serious side effects such as:

  • blood clots;
  • stroke;
  • heart attack;
  • high blood pressure; and
  • liver and gallbladder disease.

As the pill can only be obtained on prescription in Australia, your doctor will help you to decide if it is an appropriate contraception method for you. When renewing your prescription annually, your doctor will usually check your blood pressure, weight and ask about any side effects you may be experiencing.

Last Reviewed: 3 September 2013
myDr

References

1. Combined oral contraception (revised June 2009; amended October 2009, October 2010, June 2011, October 2011). In: eTG complete. Melbourne: Therapeutic Guidelines Limited; 2013 Jul. http://online.tg.org.au/complete/ (accessed Aug 2013).
2. Royal Australian and New Zealand College of Obstetricians and Gynaecologists. Combined hormonal contraceptives (updated 20 Nov 2012). http://www.ranzcog.edu.au/documents/doc_details/1173-c-gyn-28-combined-hormonal-contraceptives.html (accessed Aug 2013).
3. Family Planning NSW. The combined oral contraceptive pill (updated May 2013). http://www.fpnsw.org.au/713867_8.html (accessed Aug 2013).
4. Family Planning Victoria. The pill (combined pill) (updated Jan 2010). http://www.fpv.org.au/sexual-health-info/contraception/pills/combined-pill/ (accessed Aug 2013).
5. MayoClinic.com. Birth control pill FAQ: Benefits, risks and choices (updated 21 May 2013). http://www.mayoclinic.com/health/birth-control-pill/WO00098 (accessed Aug 2013).
myDr

myDr

myDr provides comprehensive Australian health and medical information, images and tools covering symptoms, diseases, tests, medicines and treatments, and nutrition and fitness.