Hormonal methods of contraception are very reliable, and are fully reversible once treatment is stopped.
The most popular hormonal contraception is commonly known as the pill, a small tablet that contains a combination of two sex hormones. Other methods include patches, injections, implants, and the progestogen-only pill (also known as the mini pill).
- About the pill
- Types of hormonal contraception
- Emergency contraception
- Benefits and risk of pill
- Further information
- Related topics
About the pill
The pill was launched in the UK in 1961. Nearly four million women in the UK, and 60 million women worldwide, now use the pill as a convenient and effective way to control their fertility.
If taken correctly, the pill has a 99 percent annual effectiveness. This means that if 100 women use the pill for a year, only one would be expected to become pregnant.
Conception and hormones
During a woman's monthly cycle, hormones produced by a gland in the brain cause the ovaries (small organs where the egg cells are produced and stored) to release the hormones oestrogen and progesterone. Oestrogen and progesterone cause the ovaries to release an egg (ovulation), which travels through the fallopian tube to the womb, where it can be fertilised by sperm.
Oestrogen and progesterone also thicken the lining of the womb (the endometrium) and increase its blood supply, preparing it for pregnancy. If the egg is fertilised it can implant in the lining, where it develops during pregnancy. If pregnancy doesn't occur, the levels of oestrogen and progesterone drop. The lining of the womb and the egg are shed, coming out of the vagina as a period (menstruation). It is this drop in oestrogen that makes the cycle to start again.
The combined contraceptive pill contains artificial (synthetic) versions of hormones. They mimic the action of oestrogen and progesterone on the body. When taken correctly, the pill interferes with the normal cycle to prevent pregnancy.
The pill works by:
- preventing the ovaries from releasing an egg
- thickening the mucus at the cervix (neck between the vagina and womb) making it more difficult for sperm to enter the womb and fertilise the egg
- making the lining of the womb unsuitable for a fertilised egg to implant on to
Types of hormonal contraception
Combined oral contraceptives (COCs)
Most oral contraceptives contain a synthetic version of oestrogen, called ethinylestradiol, plus a synthetic version of progesterone, known as a progestogen.
Today's pills contain either second generation or third generation progestogens. Different generations of progestogens have different risks and side effects (See Benefits and risks of the pill).
Most brands of the pill are taken for 21 days. This is then followed by a break of seven days before the next course of 21 days. The oestrogen dose can be either standard strength (30 to 35 micrograms) or low strength (20 micrograms). Some packets contain pills with two or three different doses of oestrogen which are taken at different times of the cycle. These are known as biphasic or triphasic pills, respectively.
In the UK, there are about 25 brands of pill with various hormone combinations and strengths. Certain brands, known as every day (ED) types, have 28 pills in the packet. They include seven inactive "dummy pills", removing the need for a seven day break. You just go from one packet to the next.
What to do if you forget to take the combined oral contraceptive
There are detailed instructions in the information leaflet on what to do if you miss one or more pills. If you are in doubt about what to do, don't have sex, or use condoms. Get advice from your GP or family planning nurse.
Recently, combined hormonal contraceptives have become available as an adhesive skin patch. It is worn for three out of every four weeks. When used correctly it is as effective as the combined oral contraceptive. However, it's less effective in overweight women.
Progestogen-only pill (POP)
Women who can't take oestrogen-based pills, or those who wish to avoid oestrogen, may try the progestogen-only pill. The progestogen-only pill, sometimes called the "mini pill", has a 99 percent annual effectiveness.
If you are taking the progestogen-only pill, the contraceptive effect may be lost only a few hours after a missed pill. This means the timing of the pill is crucial. It's also taken continuously rather than with a seven-day break. If you miss a pill ask a pharmacist, doctor or nurse for advice.
A single injection of a progestogen can provide contraception for up to three months. It is injected into one of the large muscles, such as the buttocks or upper arm.
The injection is as reliable as a combined pill, but fertility can take a few months to return to normal, even if the injection is not repeated. The menstrual cycle can also be unpredictable, particularly with the first injection. You can have erratic and/or heavier-than-usual periods to begin with. This can settle down to very light infrequent periods or even none at all. It has a greater than 99 percent annual effectiveness.
Progestogen implants (eg Implanon) are narrow flexible rods, about the size of a match stick. The rod is inserted under the skin of your upper arm. It releases a constant amount of progestogen, giving contraception for up to three years. The contraceptive effect reverses soon after the implant is removed. It is more than 99 percent effective over a year.
Intra-uterine system (IUS)
An IUS is a plastic frame that is placed in the womb (uterus) to prevent your eggs from reaching the sperm and being fertilized. One example is the Mirena coil. This IUS also releases progesterone to thicken the mucus making fertilisation less likely. The mirena coil is also used to treat heavy periods.
Another type of coil, the intra-uterine device (IUD) is made from plastic and copper.
If you think your contraception may have failed, emergency hormonal contraception (EHC) is available. This is a one-tablet treatment containing levonorgestrel, a type of progestogen. Although often called the "morning-after pill", it actually works for up to 72 hours after unprotected sex. But it's important to take it as early as possible. Emergency contraception prevents fertilised eggs from implanting into the wall of the womb (uterus), so stopping you from getting pregnant. EHC is available at a pharmacy under the brand name Levonelle. It is also available at family planning clinics and by prescription from your GP.
As an alternative to EHC, you can have an IUS fitted by your GP up to five days after unprotected sex. This also prevents implantation (see Intra-uterine system).
Benefits and risk of pill
You can talk to your GP or family planning nurse sbout the benefits and risks of the pill. He or she will take into account your preferences, health and family history.
The pill is a very reliable and convenient way of preventing pregnancy. It is also reversible. Fertility returns quickly when the pill is stopped.
Some other benefits of the pill are listed below.
- Use doesn't interrupt sex.
- It reduces the risk of ectopic pregnancies (pregnancies that develop outside of the uterus), which can be life-threatening.
- It protects against pelvic infection, by thickening the cervical mucus which acts as a barrier to bacteria.
- It can result in lighter, less painful periods.
- It reduces the symptoms of premenstrual syndrome.
- It reduces the risk of certain cancers such as ovarian or endometrial (affecting the lining of the womb).
- Some brands of pill can be used to treat acne and unwanted hair. Other types have no effect on these, or may make them worse.
If you have migraines or have a family history of blood clots, stroke or heart disease, seek advice before taking the pill. Taking the pill increases the risk of further complications and may not be appropriate for you.
The risk for cardiovascular disease is particularly raised if you smoke or are overweight. If you are overweight your GP may not prescribe the combined pill. He or she will suggest an alternative form of contraception, such as a contraceptive injection or progestogen-only pill (mini pill).
It's also important to realise that the pill doesn't protect against sexually transmitted diseases unlike barrier contraceptives such as the condom. It's advisable to use this additional protection with any new sexual partner. Side-effects from the pill differ among women. For most women they are minor, and can often be avoided by changing to another brand. Common side-effects are bloating, breast tenderness, headaches, acne, and mood changes.
The pill increases your risk of getting a blood clot in the legs, known as deep vein thrombosis (DVT). However, the risk of DVT is still very low,- lower than the risk of DVT naturally associated with being pregnant.
There is a slightly increased risk of breast cancer when you take the pill. However this is thought to return normal within 10 years of stopping.
Family Planning Association
- Contraception. fpa. www.fpa.org.uk, accessed 18 December 2006
- Kubba A and Guillebaud J. Combined Oral Contraceptives: Acceptability and Effective Use. Br Med Bull 1993; 49: 140-157
- British National Formulary (BNF). Contraceptives. BMJ Publishing Group, 2007. 54: 422-432
- Contraception. Clinical Knowledge Summaries. www.cks.library.nhs.uk, accessed 19 December 2006