What can affect the chances of success?


Preimplantation genetic diagnosis

The main factors affecting the chances of a successful pregnancy are:

  1. Weight (female partner)
  2. Smoking (both partners)
  3. Alcohol intake (both partners) 
  4. Folic acid intake (female partner)
  • Weight (female partner)

    If you are overweight:

    • you might not respond as well to the medication used to stimulate your ovaries and as a result produce fewer eggs
    • it is more difficult to obtain a clear scan picture during egg collection
    • the medication we give you for pain relief and sedation during this procedure can slow your rate of breathing and this can cause complications
    • if you do become pregnant, the chance of miscarriage might be higher and there can be more complications in pregnancy, in particular with high blood pressure and sugar tolerance (gestational diabetes).

    If you are underweight:

    • you may have an irregular menstrual cycle
    • you might not respond as well to the medication used to stimulate your ovaries and as a result produce fewer eggs.

    For all these reasons, we recommend that patients who are very overweight or underweight should lose or gain weight (as appropriate) before starting treatment. We will not be able to offer you treatment unless you are within the correct weight limit. If you exceed the recommended weight, we can refer you to a dietician or you can speak to your GP about local weight management programmes.

    Group weight loss programmes have been shown to be more effective than individual dieting.

    Visit the NHS webiste to find out the right weight for your height.

  • Smoking

    If you or your partner smoke we recommend you to cut down or preferably stop. Smoking has been shown to reduce the chances of conceiving naturally and lowers the success rates of IVF. Cannabis seriously affects sperm quality and reduces the chance of fertilisation.

    If you want help to try and stop smoking, please speak to your GP. Guy's and St Thomas' stop smoking service aims to help people to give up smoking. We provide advice, support and encouragement to help you stop smoking for good.

    Find out how you can stop smoking.

  • Alcohol

    Effects in men

    Excessive intake of alcohol, especially 'binge' drinking, can decrease sperm production and the number of moving sperm. Sperm take 72 days to form so the effects of damage take a long time to reverse.

    We recommend that you drink less than two units of alcohol per day.

    Effects in women

    There is no clear evidence that alcohol does or does not affect fertility in women. However as women are advised not to drink alcohol during pregnancy, preparation for PGD may be a good time to review and limit your alcohol intake.

  • Folic acid intake (female partner)

    We recommend you take 400 micrograms of folic acid each day. Folic acid is a vitamin that has been shown to greatly reduce the risk of abnormalities of the brain and spinal cord (anencephaly and spina bifida) in an unborn baby. It has no side-effects and is safe to take during pregnancy.

    Folic acid should be started by the beginning of a treatment cycle and continued to the 12th week of pregnancy. It can be bought in pharmacies and supermarkets.