Combined Oral Contraceptive Pill

How does the pill work?

The pill works mainly by changing the body's hormone balance so that you do not ovulate. That is, you do not release an egg (ovum) each month from an ovary. In addition, it causes the mucus made by the cervix to thicken and form a 'mucus plug' in the cervix. This makes it difficult for sperm to get through to the uterus (womb) to fertilise an egg. The pill also makes the lining of the uterus thinner. This makes it unlikely that a fertilised egg will be able to attach to the uterus.

How effective is the pill?

It is over 99% effective if used correctly. This means that less than 1 woman in 100 using the pill correctly will become pregnant each year. Correct use means not missing any pills, and taking extra contraceptive precautions when necessary (for example, when taking antibiotics - see below).

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.

What are the advantages of the pill?

It is very effective. It does not interfere with sex. Periods are often lighter, less painful, and more regular. It may relieve pre-menstrual tension. It reduces the risk of developing cancers of the ovary, colon and uterus (womb). In particular, the protection against cancer of the ovary is quite marked, and the protection seems to continue for many years after stopping the pill. It may also reduce the risk of pelvic infection (as the 'mucus plug' may prevent bacteria, as well as sperm, from getting into the uterus). It may help to protect against some benign (non-cancerous) breast disease. It may reduce the risk of developing certain types of cyst in the ovary.

Are there any side effects when taking the pill?

Most women who take the pill do not develop any side-effects. However, some women develop nausea (feeling sick), headaches, or sore breasts. These usually go away within days or weeks of starting the pill. If they persist, a different brand of pill may suit better.

Other side-effects are uncommon and include tiredness, change in sex drive, skin changes, and mood changes. These are unusual and you should tell your doctor or practice nurse if you have any persisting side-effects.

Blood pressure

The pill sometimes causes a rise in blood pressure. Therefore, if you take the pill you should have your blood pressure checked about every six months. The pill may need to be stopped if your blood pressure becomes high.

Who cannot take the pill?

Most women can take the pill. Your doctor or family planning nurse will discuss any current and past diseases that you have had. Some diseases cause an increased risk or other problems with taking the pill. Therefore, the pill will not be prescribed to some women with a history of certain diseases or who are at increased risk of developing certain diseases. For example, some women with an increased risk of having a blood clot (thrombosis) may be advised not to take the pill (see below).

If you are breastfeeding you should not take the pill as it can reduce the amount of milk. Other forms of contraception are available if you are breastfeeding.

Are there any risks in taking the pill?

For most woman the benefits far outweigh the disadvantages as the risks are small. However, a small number of women who take the pill develop serious problems. These include the following:

• Thrombosis which means a blood clot in a blood vessel. This can be very serious and cause a stroke, a blood clot in the lung (pulmonary embolus), or other serious problems. The following situations increase the risk of thrombosis if you take the pill. The pill may not be advised in these circumstances:
  • If you have had a previous thrombosis.
  • Severe obesity.
  • Immobility (for example, wheelchair bound).
  • Severe varicose veins.
  • Poorly controlled diabetes.
  • High blood pressure.
  • If you have a close family member who has had a thrombosis, heart attack, or stroke before the age of 45.
  • Severe migraine.
  • If you have any complications from diabetes or have had diabetes for more than 20 years.
  • Smoking - particularly if you are over 35.
  • Some other rare conditions.
  See a doctor straight away if you have any of the following: severe headache, bad pains in the chest or leg, leg swelling, breathing difficulty, if you cough up blood, sudden problems with sight or speech, weakness or numbness in an arm or leg, collapse.
• Cancer. There is a small increased risk of developing breast cancer in women who use the pill. Some studies also suggest a possible link between the pill and a slight increased risk of cancer of the liver or cervix. These have to be balanced against the much reduced risk of developing cancer of the ovary, and of the reduced risk of developing cancer of the uterus and colon mentioned in 'advantages'. When all cancers are grouped together, the overall risk of developing a cancer is reduced if you take the pill.

How do I take the pill?

There are different brands of pill which contain varying amounts and types of oestrogen and progestogen. There is usually a leaflet inside the packet of pills. Read the leaflet carefully and make sure you understand how to take the pill and what to do in special situations such as if you miss a pill or vomit. The following gives a general guide.

Brands with 21 day pills

Most brands of pill come in packs of 21. To start, it is best to take the first pill on the first day of your next period. You will be protected against pregnancy from then on. If you start the pill on any other day, you need an additional contraceptive method (such as condoms) for the first seven days. Take your pill at about the same time each day for the 21 days.

You then have a break of seven days before starting your next pack. You will usually have some bleeding in the seven day break. This is called a 'withdrawal bleed' and is like a period, although strictly speaking it is not a 'menstrual period'. You will be protected from pregnancy during the seven day break provided you have taken your pills correctly and you start the next pack on time. Start the next pack after the seven day break whether you are still bleeding or not. If you take the pill correctly, you will start the first pill of each pack on the same day of the week.

Most 21 day pills have the same amount of oestrogen and progestogen in each pill. Some brands called phasic pills vary the dose in two or three steps throughout the 21 days. The pills in these packets have to be taken in the correct order as directed on the packet.

Brands with everyday pills

These contain 21 active and seven 'dummy' pills. Instead of a seven day break, you carry on taking the dummy pills. The idea is that you don't have to remember to re-start the pill after a seven day break. So, you get in a routine of taking a pill everyday. The pills have to be taken in the correct order. Read the instructions carefully, particularly on when to start, which pill to start with, and how long it takes for the contraceptive effect to begin.

What if I miss or forget to take one or more pills?

Read the leaflet that comes with your brand of pill for advice on what to do. Ovulation (and therefore pregnancy) may occur if you miss pills, particularly if the missed pills are at the end or beginning of the packet. Generally, the advice depends on how many pills you have missed, and when they were missed in the cycle.

If you are unsure as to what to do, or if you are unsure that you have taken the pill correctly, then use other forms of contraception (such as condoms) and seek advice from a doctor or nurse.

Do other medicines interfere with the pill?

Yes, some do but most do not. Therefore, before you take any other medicines, including those available to buy without a prescription, herbal and complementary medicines, ask your doctor or pharmacist if they stop the pill from working properly. He or she will advise you what to do. For example, certain antibiotics are the most common example of medicines that can stop the pill from working properly. Other examples include some medicines that are used to treat epilepsy and TB. St John's Wort is an example of a commonly used herbal remedy that can affect the pill.

Antibiotics

Your doctor will normally advise on what to do if you are prescribed an antibiotic. Generally, when prescribed a short course of antibiotics (up to three weeks) you should carry on taking your pill. But, in addition, you should use another method of contraception (usually condoms) whilst you are on the antibiotics, and also for a further seven days after you have finished the course of antibiotics.

Further, when you stop the course of antibiotics, if you have less than seven pills left in the packet you should not have the usual seven day break from taking the pill. You should start the next packet straight away. (If you are taking an 'everyday' brand and you have less than seven active pills left, then throw away the dummy pills and go straight onto the active pills of the next packet.)

Further, if you are in the first week of your pill packet, and you start some antibiotics, and you have had sex in the last few days, then seek advice from your doctor or nurse. You may need emergency contraception.

For long courses of antibiotics such as those given for acne, ask your doctor for advice.

What if I vomit or have diarrhoea?

If you vomit within 2-3 hours of taking a pill, the pill will not have been absorbed. If you are well enough, take another pill as soon as possible. Provided that you do not vomit this second pill and it is taken on the same day, then you will remain protected from pregnancy. If you continue to vomit, then it is the same as 'missing pills' (see above).

Mild diarrhoea does not affect the absorption of the pill. Severe diarrhoea may do so, and so if you have severe diarrhoea, consider this as the same as 'missing pills' (see above).

What happens if I don't have a withdrawal bleed (like a period) between packs?

It is normal to have bleeding (like a period) during the seven day break between pill packs (or when taking the 'dummy' pills in everyday pills). However, it is quite common for there to be no bleeding between pill packs. You are not likely to be pregnant if you have taken the pill correctly and have not vomited or taken any medicines that can interfere with the pill. Start the next pack after the usual seven day break and continue to take your pill as usual.

See your doctor or nurse if: you don't have any bleeding after the next pack (two packs in total), or you have not taken the pill correctly, or you have any reason to think that you may be pregnant. A pregnancy test may be advised.

Bleeding whilst on the pill (breakthrough bleeding)

During the first few months while your body is adjusting to the pill you may have some vaginal bleeding in addition to the usual bleeding between packs. This is not serious but more of a nuisance. It may vary from 'spotting' to a heavier loss like a light period. Do not stop taking your pill. This usually settles after the first 2-3 months. If it persists, see your doctor or nurse. Another brand of pill may be more suitable for you.

Can I delay or skip a withdrawal bleed (period)?

There are times when it is useful not to have vaginal bleeding (a 'period' between packs). For example, during exams or holidays. Check with your doctor or nurse about the best way to do this with your particular brand of pill. For the commonly used pill types (that is, not 'bi-phasic' or 'tri-phasic' or 'everyday' types) you can go straight into your next pack without a break. Have the usual seven day break at the end of the second packet. If you just want to delay the withdrawal bleed, begin the new pack without the seven day gap and when you want your bleeding to start, stop taking the pill. Have a seven day gap in the usual way and then start a new pack after this. (You should only do these modifications now and again as regular monthly withdrawal bleeds are normally recommended.)

Further information

Your GP, practice nurse, family planning clinic and pharmacist are good sources of information if you have any queries.

The fpa (formerly the family planning association) also provide information and advice.
fpa's helpline: 0845 310 1334 or visit their website www.fpa.org.uk