There are two groups of combined contraceptive pills currently under discussion:

1. The "older" pills containing either levonorgestrel or norethisterone i.e. Microgynon, Ovranette, Logynon, Loestrin, Trinovum, Trinordiol, Brevinor, Norimin.
2. The "newer" pills, containing desogestrel or gestodene i.e. Mercilon, Marvelon, Femodene, Minulet, Triadene and Triminulet.

Another pill, Cilest, contains a different hormone that has not been used for long enough to be included in the recent studies.

Pills and clots

The recent news has concerned the risk of having a venous thrombo-embolism (clot) whilst taking the pill. Studies have suggested that this is more likely with the newer pills (group 2 above) than the older pills (group 1).

The relative risks of venous thrombo-embolism in women are as follows:

Less than 2 women in 100 who have a venous thrombo-embolism die as a result of it, so the risk of dying from a venous thrombosis due to either group of pills is less than 3 per million pill users per year. This is a tiny risk. Compare this to the risk of dying from smoking.

Other complications

The recent studies did not consider the increased of heart attack or stroke for each group of pills. Heart attacks and strokes are more common than venous thrombosis and are much more likely to result in death. To give you some idea of this consider the following. In 1989, among 11 million women aged 15-44 in England and Wales, there were 18 death from venous thrombosis (all causes combined, not just pill users), compared with 260 from heart attack and stroke.

The group of newer pills (group 2) contains hormones that are "lipid and carbohydrate friendly." They do not alter your blood cholesterol in a manner likely to cause heart and blood vessel disease. They are less likely to increase your risk of heart attacks and strokes than the older group of pills.

Other considerations

All combined oral contraceptive pills reduce the risk of ovarian and womb cancer, pelvic infection and. of course, pregnancy and its complications. You must also take into account the "minor" side effects of the pill, such as break-through bleeding, acne, headaches and weight gain—symptoms which tend to benefit from the newer group of pills. You can see that if you understand your personal level of risk of serious side effects from your combined pill, you will be in a much stronger position to decide which pill to have, and will be able to feel confident about your choice.

Conclusions

In order to decide which pill is safest for you to take, you must consider your own personal risk factors.

• Group 1—women who should not be prescribed any combined oral contraceptive includes:
  • all women with a personal history of venous thrombo-embolism
  • those women with complicated diabetes mellitus
  • those women with high cholesterol.
• Group 2—women whose most important risk is that of thrombo-embolism and who should consider taking the older group of pills includes:
  • healthy, low risk women under 30 years of age
  • those with severe varicose veins
  • those who have a family history of venous thrombosis
  • those who are immobile
  • those who are overweight (body-mass index over 30kg/m2).
• Group 3—women whose most important risk is that of heart attack or stroke and who should consider taking the newer group of pills includes:
  • heavy smokers (more than 10/day)
  • those with high blood pressure
  • those with a close family history of heart attack or stroke
  • those with uncomplicated diabetes mellitus
  • women over the age of 30 years.

References

This information sheet is based on an editorial in the British Medical Journal, published 28/10/95 written by John Guillebaud, Professor of Family Planning and Reproductive Health, Margaret Pyke Centre, London.