Answers to questions women ask about clots

What is a blood clot (also known as thrombosis)?

The blood clots associated with oral contraceptives occur in the veins of the legs and cause a blockage. This may cause death when pieces of the clot dislodge and travel to the lungs, but this happens rarely.

How do third-generation pills differ from earlier pills?

They contain progestogens called desogestrel or gestodene. They came on the market in the 1980s promoted as more easily tolerated by women, and causing fewer side-effects such as weight gain and skin problems.

How often do blood clots occur with oral contraceptives?

Blood clots rarely occur with oral contraceptives, and deaths from blood clots are even more rare.

The risk of a healthy woman developing a blood clot in one year is one in 30,000. The risk is increased by pregnancy.

How often are blood clots fatal?

Of those who get a blood clot, 1 to 2 per cent will die. One death in about two years would be expected in New Zealand women using oral contraceptives, hence the alarm over the seven deaths in seven years revealed in 1999.

What increases the risk of blood clots?

Some of the factors are a previous blood clot, a close family member who has had a blood clot, bad varicose veins, being overweight, a smoker, or being immobilised.

What are the symptoms and what should I do about them?

The symptoms of a blood clot in the leg are swelling, tenderness and pain, but a clot may occur without symptoms. Breathlessness occurs with a blood clot on the lungs.

If you are taking an oral contraceptive pill and you develop any of these symptoms you should see a doctor immediately.

Who could I discuss this with?

With your doctor, before going on an oral contraceptive pill.

You have a right to expect your doctor to explain the risks to you, but remember that blood clots are rare events in healthy women taking the pill.