Royal Prince Alfred Hospital
Fertility Unit
Royal Prince Alfred Hospital


It is important to be in a healthy weight range when undergoing fertility treatment. Being considerably overweight or underweight can adversely affect the outcome of your fertility treatment.

We use Body Mass Index (or BMI) to determine whether you are in a healthy weight range.

What is BMI?

BMI is a formula that takes into account your weight and height.

  • A high BMI indicates that you are overweight in relation to your height.
  • A low BMI indicates that you are underweight in relation to your height.

How does a high BMI affect my fertility treatment?

Recent research has shown that just a small amount of weight loss (4-5 kilos) can improve your chance of spontaneous ovulation leading to pregnancy and your chance of pregnancy with IVF treatment.

If you are overweight, it may be more difficult to see your ovaries on ultrasound. As a result your egg collection may take longer, be more painful and the doctor may not be able to access all of your eggs. In extreme cases, we may not be able to access the ovaries at all.

Excess weight can also cause complications during pregnancy such as:

  • Miscarriage
  • Diabetes
  • Premature labour
  • High blood pressure / toxaemia
  • Infection (post-delivery)
  • Difficulties with breast feeding
  • Foetal Abnormalities

How does a low BMI affect my fertility treatment?

Patients who are very underweight often stop ovulating. If you are underweight you have an increased risk of developing ovarian hyperstimulation syndrome. If you become pregnant, there is a greater risk of premature birth and a low birth-weight baby.