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BMI and Healthy Pregnancy Weight

Information from the Healthy Pregnancy & Me brochure for pregnant women on BMI and guidelines around healthy weight gain during pregnancy.

What is BMI?

Body Mass index (BMI) is a way of estimating if you are likely to have a healthy body weight compared to your height (i.e. determine whether your weight is healthy for your height).

While a person's BMI is just a guide, it is useful tool for goal-setting for a healthy pregnancy weight.

You can calculate your own BMI using the calculator below:

What does "Healthy Pregnancy Weight" mean?

Pregnancy weight is the weight gained during pregnancy. The pregnancy weight that results in the best pregnancy and birth outcomes for women and their babies is considered to be "healthy".

Therefore, Healthy Pregnancy Weight is the amount of weight that you can gain to optimise the health outcomes for both yourself and your baby. So, in order to achieve the best possible pregnancy and birth outcomes it is important to manage your weight gain in pregnancy.

How do I know how much to gain?

Thanks to extensive research, involving thousands of pregnant women of different weights and sizes, there are recommendations available that help women to know what is healthy for them. Staying within these pregnancy weight gain recommendations will not only reduce the risk of complications for you and your baby during pregnancy and the birth but also improve your weight status post-birth.

The healthy pregnancy weight recommendations are based on your pre-pregnancy BMI and take into account:

- The weight of your baby and the supporting structures such as the placenta and uterus - these weigh a similar amount for all women regardless of their pre-pregnancy BMI.

- The changes in your body's composition to support your pregnancy - these vary depending on your body composition before becoming pregnant.

- Differences in pregnancy weight recommendations relate to the amount of extra weight needed to accommodate breastfeeding. Women with a normal pre-pregnancy BMI (18.5-24.9 kg/m2) will probably need to gain more weight to support the energy burden of breastfeeding than women with a raised BMI (greater than 30 kg/m2).

What Are the Healthy Pregnancy Weight Recommendations?


Source: Institute of Medicine (IOM) and National Research Council (NRC) *For single pregnancies only (i.e. not twins, triplets)

Why is achieving a healthy pregnancy weight important?

Research tells us that having a healthy pregnancy weight can substantially reduce the health risks for mothers and babies during and after pregnancy. By staying within your optimum weight range during pregnancy you can also improve how your body functions, provide a better environment for your unborn baby and help reduce the potential risks in labour and recovery.

The recommendations also take into account the normal changes that happen to your body to accommodate your baby's growth (e.g., production of amniotic fluid & the placenta). So even if some of the weight goals seem low, in following them, there is no risk of not providing your baby of the nutrients and energy it needs.

I know my weight goal, what do I do now?

Firstly, remember that having a healthy pregnancy weight is achievable. Healthy pregnancy weight goals do not mean restrictive dieting and extreme exercising- achieving them is about re-assessing your lifestyle habits, identifying small and sustainable changes, and taking steps to implement them.

In combination, you may find they can have a surprisingly large effect on not only your weight but also your emotional and physical wellbeing. Not to mention your child's health, so keep in mind the benefit you are providing to your baby.