Shaping up for conception

The links between being overweight or obese and an increased risk of chronic diseases, such as heart disease and diabetes, are well known - we read about them all the time.

But what’s less well publicised is that an unhealthy weight – in either partner – can also have a significant impact on your ability to conceive.

"Obesity can cause problems from conception right through to delivery and beyond," Genea Oxford Women’s Health Medical Director, Dr Richard Dover says.

"An unhealthy weight in both women and men can affect fertility and delay the time it takes for a woman to fall pregnant."

The Fertility Factor - Could being overweight be stopping me from falling pregnant?

Being overweight or obese not only reduces the chances of a couple conceiving naturally, but also means fertility treatment, such as IVF, is less likely to be successful. So you may need to diet to increase fertility. During pregnancy, it can also lead to complications including gestational diabetes and an increased risk of miscarriage, stillbirth, birth defects and obstetric complications.

Being underweight can also harm a woman’s ability to conceive.

The main effect of weight on fertility in women is due to a failure to ovulate - anovulation. There are also other more subtle metabolic effects due to elevated insulin. Women with a Body Mass Index (BMI) of 25-30 are 50 per cent more likely to have anovulatory infertility than women with a normal BMI. This rises to 300 per cent for women with a BMI over 30. Unfortunately, IVF success rates may be reduced by as much as 25 per cent in obese patients and 50 per cent in very obese patients. You can check your BMI on our calculator.

What’s my BMI?

Your BMI or Body Mass Index is calculated from your weight and height - it’s one way to determine body fat. You can use our BMI calculator on the righthand side of this page to figure out yours.

In both men and women, a BMI:

  • over 30 is considered obese;
  • between 25 and 29.9 is considered overweight;
  • between 18.5 and 24.9 is considered a healthy BMI; and
  • under 18.5 is considered underweight.

The good news

Fortunately, losing weight can help improve your chance of conceiving and minimise your risk of having complications if you do fall pregnant.

Approximately 90 per cent of overweight women will resume ovulation if they lose as little as five per cent of their original weight and 30 per cent will conceive naturally. In very obese women this is a higher pregnancy rate than can be achieved with a single IVF cycle. The success rates for IVF and other forms of assisted reproduction also improve dramatically with weight loss.

So the good news is that weight loss itself can be an effective fertility treatment and many of our patients conceive naturally after focusing on their diet and trying to exercise more.

Next steps

If you've used our BMI calculator and found your weight range may be slightly outside the 'ideal'; weight range there is some value in working to achieve a more healthy range.

Healthy food choices and exercise go hand in hand. You may also wish to speak to our fertility specialists who can provide you with more information and advise you on a course of action.