If you are a woman and very overweight, your doctor may advise you to lose weight before having fertility treatment. Doctors have been told to delay offering in vitro fertilisation (IVF) treatment to women who are very overweight (obese), until they can get down to a healthy weight.^[24]

This may sound very unfair. But there are good reasons why it may be best to try to lose weight before having fertility treatment.^[24]:

• Some fertility problems are caused by being overweight. Being very overweight can disrupt your hormones, so you don't release eggs (ovulate). If you lose weight, you may find you can get pregnant naturally, without having treatment.

• Fertility treatments like IVF put quite a lot of strain on the body. Some treatments can be harder to do if a woman is very overweight. Your doctor may think the treatment is too much of a risk for your health, if you are very overweight.

• Fertility treatments like IVF work better if you are at a healthy weight. Being at a healthy weight means you are more likely to get pregnant with fertility treatment.

• Being overweight means you are more likely to have problems in your pregnancy, such as miscarriage, high blood pressure, problems with labour, and diabetes. Babies are also at more risk of birth defects if their mothers are very overweight.

Doctors measure people's weight using body mass index. This is a single number that says whether you are a healthy weight for your height. A BMI of 18.5 to 25 indicates a normal, healthy weight. A BMI of 25 to 30 shows you are overweight. If your BMI is 30 or over, doctors will say you are obese. You can work out your BMI here.

Guidelines say that women under the age of 37 should have their treatment delayed until their BMI is less than 30. Women over the age of 37 should have treatment delayed until their BMI is less than 35. ^[24]

Your doctor should offer you help and support to get your weight down to a healthy level. For more about what works best, read our information on Obesity.

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