How does the progestogen-only contraceptive pill work?
The progestogen-only contraceptive pill (POCP) contains a progestogen hormone. This is similar to the progesterone hormone made by the ovaries. It works mainly by thickening the mucus made by the cervix, which forms a plug in the cervix. This stops sperm from getting through to the womb (uterus) to fertilise an egg. The POCP also makes the lining of the womb thinner. This makes it unlikely that a fertilised egg will be able to implant in the lining of the womb. It also has some effect on the ovary. Ovulation (the release of an egg each month) may not occur as often when you take the POCP. One type of POCP, Cerazette®, stops ovulation in more than 9 out of 10 women.
How effective is the progestogen-only contraceptive pill?
The POCP is 99% effective if taken correctly. This means that 1 woman in 100 using the POCP correctly will become pregnant each year. (Compare this to when no contraception is used. More than 80 in 100 sexually active women who do not use contraception become pregnant within one year.) Correct use includes taking it at the same time every day. If it is not taken correctly, more women will become pregnant.
What are the advantages of the progestogen-only contraceptive pill?
It does not interfere with sex. You can take it when you are breast-feeding. The risks associated with the oestrogen in the combined pill (for example blood clots) do not occur. It can therefore be used by some women who cannot take the combined pill. For example, if you are aged over 35 and smoke, if you have migraines, if you have high blood pressure.
What happens to your periods when you take the progestogen-only contraceptive pill?
The effect on periods can vary. Some women taking the POCP continue to have regular normal periods. However, some have irregular periods and some have very infrequent, or no, periods. Some women also have occasional ‘spotting’ between periods.
Changes in bleeding patterns when taking the POCP are common:
- 2 in 10 women have no bleeding.
- 4 in 10 women have regular bleeding.
- 4 in 10 women have irregular bleeding.
You should continue to take the POCP everyday, including when you have periods. However, if you do develop irregular bleeding while taking the POCP, you should inform your doctor. Irregular bleeding can sometimes be due to another reason – for example an infection, which may need to be treated.
Are there any side-effects with taking the progestogen-only contraceptive pill?
Side-effects are uncommon. If one or more do occur, they often settle down over a couple of months or so. Examples of possible side-effects include: mood swings, reduced sex drive, increase in acne and breast discomfort.
Who cannot take the progestogen-only contraceptive pill?
Most women can take the POCP. Your doctor or family planning nurse will discuss any current and past illnesses. For example, you should not take the POCP if you have recently had breast cancer, have hepatitis or take certain medications.
How do I take the progestogen-only contraceptive pill?
Start taking the pill on the first day of your next period. It is immediately effective from then on. If you start on any other day, you should use additional contraceptive methods (such as condoms) for the first two days (until the POCP has become effective). If you have just had a baby, the POCP is immediately effective if you start taking it before day 21 after the birth. There are different brands of POCP.
You should take the POCP at the same time of day, every day. Any time of day will do, but the most important thing is to get into a routine. Do not stop taking it when you have a period. You should take it every day. When you finish one pack, start another the next day. If you take a pill more than three hours later than usual (12 hours for a POCP called Cerazette®), you lose protection (see below).
What if I forget to take a pill?
If you forget a pill, take it as soon as you remember. If you are more than three hours late in taking it (12 hours for Cerazette®) then your protection immediately fails. Continue taking your pill each day, but you will need to use extra contraception for two days (such as condoms) until the POCP becomes effective again.
What if I am ill with vomiting or diarrhoea?
If you vomit within three hours of taking your POCP or have severe diarrhoea, the pill will not be absorbed. Carry on taking the POCP as usual, but you will need to use other forms of contraception (such as condoms) for the duration of the illness plus for a further seven days after the vomiting or diarrhoea has stopped.
Do other medicines interfere with the progestogen-only contraceptive pill?
Some medicines may interfere with the POCP and make it less effective. Examples of these include anti-epilepsy medicines (which are sometimes used as painkillers), antifungal treatment and St John’s wort. Tell the doctor or pharmacist that you take the POCP if you are prescribed or buy another medicine.
Your GP, practice nurse, and pharmacist are good sources of information if you have any queries.
The fpa (formerly the family planning association) also provides information and advice.
fpa’s Helpline: 0845 310 1334 or visit their website: www.fpa.org.uk
References and Disclaimer | Provide feedback