How does it work?
The main action of the hormones in the combined pill is to stop the ovary releasing an egg each month (ovulation). They also thicken the fluid (mucus) at the cervix so sperm cannot enter the womb, and alter the lining of the womb to make it less likely to accept a fertilised egg.
How effective is it?
As with any contraceptive, its effectiveness depends on how well the instructions are followed. With perfect use, the combined pill is over 99% effective meaning that less than 1 woman out of 100 will become pregnant in a year. However, because many women occasionally forget to take the pill, the actual failure rates vary and can be up to 8%.
Who is the combined pill suitable for?
Not everyone can use the combined pill so your doctor or nurse will need to ask you about your own and your family’s medical history to ensure that the pill is suitable. Mention any illnesses or operations you have had and whether you are a smoker.
Some conditions which may mean you should not use the combined pill are:
- You smoke and are 35 or over.
- You are 35 or over and stopped smoking less than a year ago.
- You are breastfeeding.
- You are very overweight.
You have now or have had in the past:
- Thrombosis (blood clots) in any vein or artery
- A heart abnormality or circulatory disease, including raised blood pressure (hypertension)
- Current breast cancer or breast cancer within the past 5 years
- Migraine with aura
- Disease of the liver or gallbladder
- Diabetes with complications
If you are healthy, don’t smoke and there are no medical reasons for you not to use the combined pill, you can use it until your menopause. However, as the risks of cardiovascular disease increase with age, doctors often recommend changing after the age of 40.
The combined pill should be started between the first and fifth days of the menstrual cycle. If started on day one or two no other contraceptive is needed. If started on any other day, extra precautions (i.e. avoid sex or use condoms) should be used for the first seven days. Take the pills daily to the end of pack.
What should I do if I forget to take a pill?
If you are less than 12 hours late:
- Take the missed pill as soon as you remember it and carry on with the rest of the pack as normal. No extra precautions needed.
If you are more than 12 hours late:
- Take the missed pill as soon as you remember and carry on with the rest of the pack as normal (you may need to take two pills together). You will need to use extra precautions for the next seven days. If you have unprotected sex during this time you may need emergency contraception. If you have less than seven pills left in your pack, do not take your seven-day break this month. Start your new pack on the day after finishing the current pack. The withdrawal bleed will probably not occur in this case.
There are different types of packs. Some packs have 28 pills and you should not take a break between packs. Other packs have 21 pills and you should take a seven-day break between packs. Withdrawal bleeds (pill period) will either happen at the end of a 28-day pack or during seven-day break if using 21-day packs.
Are there any side-effects?
When starting the pill some women may experience: breast tenderness, skin irritation, mild headaches, a bloated feeling, or have some breakthrough bleeding (bleeding between periods). Although these can be a nuisance, they are not dangerous and should disappear within the first few months of using this contraceptive. There are rarely more serious side effects. Some women could develop a blood clot in the leg or lung and some may develop severe migraine.
You should see a doctor immediately if you develop any of the following symptoms:
- Pain or swelling in the legs.
- Severe chest pain.
- Breathlessness or coughing up blood.
- Bad fainting attack or collapse.
- Unusual headaches or difficulty with speech or sight.
- Numbness or weakness of a limb.
Can other medication interfere with the pill?
Evidence shows that antibiotics do not affect the combined oral contraceptive pill as long as pills are taken correctly and no vomiting or diarrhoea occurs. However, liver enzyme-inducing medication such as HIV treatments or epilepsy medication may make the combined contraceptive pill less effective. As with any medicines tell your doctor if you are using hormonal contraception. The complementary medicine St John’s Wort may also make the combined contraceptive pill less effective.
Ask your doctor for advice about your pill use if you are planning to have surgery, are immobilised for a prolonged time, are taking a high altitude holiday or a long-haul flight. The pill, like most methods of contraception, does not protect against sexually transmitted infections (STIs). Condoms, when used correctly and consistently, can help protect against STIs.
What if I become pregnant?
There is a slight chance you will become pregnant even if you use the pill correctly. However, a missed period does not always mean you are pregnant, especially if you have used the pill correctly. If you think you have put yourself at risk of pregnancy or if you miss a second period see your doctor at once.
You can start taking the pill three weeks (21 days) after giving birth. Starting on day 21 you will be protected against pregnancy straight away. If you start later than day 21, you will need to use an extra method of contraception for seven days. If you are breastfeeding, taking the combined pill may reduce your flow of milk. It is usually recommended that you use a different method of contraception.
After an abortion or miscarriage
You can start taking the combined contraceptive pill immediately after a miscarriage or abortion, if you were pregnant for less than 24 weeks. You will be protected from pregnancy straight away.