The progestogen-only contraceptive pill (POP) is an effective method of contraception if used correctly. It is commonly used when the combined pill (which also contains oestrogen) is not suitable. It can also be safely taken if you are breast-feeding.
How does the progestogen-only pill (POP) work?
The POP contains a progestogen hormone. This hormone is similar to the progesterone hormone made by the ovaries. The progestogen hormone in older (traditional) POPs is either levonorgestrel or norethisterone. Brands currently available in the UK are Micronor®, Noriday® and Norgeston®. A newer type of POP contains a progestogen hormone called desogestrel. Brands currently available are Cerazette®, Aizea®, Cerelle® and Nacrez®.
Older POPs work mainly by thickening the sticky mucus made by the neck of the womb (cervix). The mucus forms a plug in the cervix. This stops sperm from getting through to the womb (uterus) to fertilise an egg.
POPs also have some effect on the ovary. Your ovaries do not release an egg (ovulate) as often when you take the POP. The newer type of POP containing desogestrel stops ovulation most of the time. Stopping ovulation is the main way these newer pills work.
How effective is the progestogen-only pill (POP)?
Between 3-80 women in 1,000 using the POP will become pregnant each year. (If no contraception is used, more than 800 in 1,000 sexually active women become pregnant within one year.) Correct use gives the lower figure (3 per 1,000) and includes taking the pill exactly according to instructions, at the same time every day. If it is not taken correctly, more women will become pregnant (80 per 1,000).
What are the advantages of the progestogen-only pill (POP)?
- Taking the POP does not interfere with sex.
- You can take it when you are breast-feeding.
- It has a lower dose of hormone than the combined pill.
- The POP does not give you a higher risk of blood clots (unlike the combined pill.) 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, or if you have high blood pressure.
What are the disadvantages of the progestogen-only pill (POP)?
- You have to remember to take the pill at exactly the same time every day. For older POP brands, this means within three hours of the time you took it the day before; for POPs containing desogestrel, within 12 hours.
- It can give you irregular periods. See the section below.
- It can give you some side-effects, although these are usually mild. See the section on side-effects.
- It cannot be taken with some kinds of other medication. See the section about other medication which interferes with the POP.
- It may mean you are more likely to develop cysts in your ovaries. If this happens they are usually small and do not need any treatment.
- It may (like the combined pill) give you a very small increased risk of breast cancer.
What happens to your periods when you take the progestogen-only pill (POP)?
The effect on periods can vary. Some women taking the POP continue to have regular normal periods. However, some have irregular periods, some have very infrequent periods, and some have no periods. Some women also have occasional 'spotting' between periods.
Changes in bleeding patterns when taking the POP 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 POP every day, including when you have periods. However, if you do develop irregular bleeding while taking the POP, 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 pill (POP)?
Side-effects are very 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, headaches, feeling sick, increase in acne and breast discomfort.
Who cannot take the progestogen-only pill (POP)?
Most women can take the POP. Your doctor or family planning nurse will discuss any current and past illnesses. You should not take the POP if you have breast cancer, or have had it in the past. You also should not take it if you have very severe liver disease, or liver tumours. If you take certain medications you may not be able to take the POP, especially if you are on medication for epilepsy. See the section on other medicines below.
How do I take the progestogen-only pill (POP)?
Start taking the pill on the first day of your next period. It is immediately effective from then on. It will also start to work straightaway if you begin taking it up to the fifth day from the start of your period. (ie if Day 1 is the first day of your period, you can begin taking it on Day 1, 2, 3, 4 or 5 and it will work straightaway.) If you start on any other day, you should use additional contraceptive methods (such as using condoms or not having sex) for the first two days. This is until the POP has become effective.
If you have just had a baby, the POP is immediately effective if you start taking it before day 21 after the birth. If you begin taking it after Day 21, use additional contraception (eg, condoms or not having sex) for two days.
You should take the POP 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 for the traditional pills, you lose protection (see below). If you are taking a newer pill containing desogestrel, you have a 12-hour window to take your pill. If you are more than 12 hours late, you will need to use extra protection.
What if I forget to take a pill?
If you forget to take a progestogen-only pill (POP), take it as soon as you remember. If you are more than three hours late in taking it (or more than 12 hours with a desogestrel POP) then your protection immediately fails. Continue taking your pill each day, but you will need to use extra contraception (such as condoms) for two days until the POP becomes effective again.
What if I am being sick (vomiting) or have diarrhoea?
If you vomit within two hours of taking your progestogen-only pill (POP) or have severe diarrhoea, the pill will not be absorbed. Carry on taking the POP as usual, but use other forms of contraception (such as condoms) for the duration of the illness plus for a further two days after the vomiting or diarrhoea has stopped.
Do other medicines interfere with the progestogen-only pill (POP)?
Some medicines may interfere with the POP and make it less effective. Tell the doctor or pharmacist that you take the POP if you are prescribed or buy another medicine. Medicines which interfere with the POP include:
- Some medicines for epilepsy. For example carbamazepine, oxcarbazepine, eslicarbazepine, phenytoin, phenobarbital, primidone, and topiramate. Some of these pills are used for other problems - eg, migraine or pain.
- The antibiotics rifampicin and rifabutin. (Other antibiotics do not affect the POP.)
- Some medicines used to treat HIV and AIDS. For example nevirapine and ritonavir.
- St John's wort. This is a treatment bought over-the-counter, and sometimes used for depression. Your doctor may not know you are on it, so you should mention it. The POP may not work if you are taking St John's wort.
- Ulipristal acetate. This is a medicine which comes in two forms - as ellaOne® for emergency contraception, and Esmya® for fibroids. If you take the POP after using ellaOne®, you should also use additional contraceptive precautions until your next period starts. If you take Esmya® you should not use the POP. You should also not take it for 12 days after finishing it.
Further help & information
Dr Tim Kenny
Dr Mary Harding
Prof Cathy Jackson