BMI for pregnancy

As a woman’s weight can affect fertility across both ends of the spectrum, your body mass index (BMI) is a useful way of identifying if your weight is within a healthy range. Find out what an ideal BMI is for pregnancy.

Description/explanation of BMI

Your Body Mass Index (BMI) is a useful tool to estimate whether you are underweight, overweight or at a healthy weight in relation to your height.

As your weight increases or decreases out of the healthy weight range, it can increase your risk of health problems and may make it harder for you to conceive.

Calculate your BMI...

Relationship between BMI and pregnancy fertility

Weight can affect a woman's fertility across both ends of the spectrum.

Being underweight can also reduce a woman’s fertility as it can cause a hormone imbalance that affects ovulation and therefore a woman’s chance of getting pregnant. Having a BMI under 18.5 is considered ‘underweight’.

Being overweight impacts a woman’s chance of conceiving and having a healthy baby. It can cause a hormone imbalance, triggering problems with menstruation and ovulation. When women who are overweight do conceive, they have a higher risk of pregnancy complications e.g. miscarriage, diabetes or premature birth.

The father’s weight can also affect your chances of getting pregnant, so it’s important that they too maintain a healthy BMI.

What's involved in a fertility consultation?

A conversation with a fertility specialist can help you understand your overall reproductive health. They will organise a few simple tests to identify any factors that could be affecting your fertility.

For women these usually involve blood tests and an ultrasound and for men a semen analysis.

What is an ideal/healthy BMI for conceiving?

A healthy BMI range is between 18.5 to 24.9 for young and middle-aged adults. Under 18.5 is considered underweight and over 25 is overweight. If a woman's BMI is greater than 35, the risk of problems become more significant. We recommend speaking to your Doctor if you have any concerns.

What to do if you're not in the ideal BMI range?

It’s very common to be struggling with your weight, but also wanting to become a mother.  It’s particularly frustrating because you can see that some women with weight problems can conceive quickly (although the risks in the pregnancy are still significant). Nonetheless, even though it’s not easy, it is still worth doing whatever you can to try and lose weight before you start trying for a pregnancy.  Even losing a few kilos can make that pregnancy quicker and easier. One target that has been suggested is to try and lose 5% of your bodyweight.

If your problem is that you are underweight, you should seek some assistance in gaining weight before you start to conceive as there is good evidence that being underweight at the time of conception can affect your baby’s birthweight.

It’s never easy to change your weight but for a safe pregnancy and a healthy baby, it really is worth striving to achieve whatever you can. Do ask for help. 

Book a fertility consultation

It is recommended you seek specialist advice if you have been trying to conceive for 12 months (6 months if you are over 35), or you are considering trying to conceive.

To book an appointment simply complete the form below or call 1800 111 483.