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Weight gain in pregnancy

10-minute read

Key facts

  • You are likely to gradually gain weight during your pregnancy as your baby grows and your body changes.
  • How much weight you gain during your pregnancy depends on your weight pre-pregnancy, and other factors.
  • Putting on more than the recommended amount of weight during pregnancy can lead to complications for you and your baby.
  • You can determine how much weight you should gain by using your pre-pregnancy BMI, and by talking to your doctor or midwife.

Will I gain weight during my pregnancy?

As your baby grows, you are likely gradually gain weight.

You should be mindful of your weight gain during pregnancy. Gaining more or less weight than is recommended can impact the health of you and your baby.

If you have concerns about your weight gain during pregnancy, discuss this with your doctor or midwife.

Some people may lose weight early in their pregnancy because of morning sickness. However, if you had a normal or low BMI before pregnancy, you will gradually put on weight over the course of your pregnancy.

Why am I gaining weight while pregnant?

Not only is your baby growing, but your body is also developing extra body tissue and retaining more fluid. This is for:

  • the amniotic fluid around your baby
  • your baby’s circulation
  • placenta

You may also gain more weight if you are having more than one baby.

During pregnancy, your appetite may change. You may crave some foods, and not be able to stomach others. This can also affect your weight gain.

What is normal weight gain in pregnancy?

The average pregnant person gains between 11.5kg and 16kg of weight during pregnancy. But, how much weight you should gain will depend on how much you weighed before your pregnancy, and other factors.

To calculate how much weight you should gain, you can start by determining your pre-pregnancy body mass index (BMI).

Calculating your body mass index

Your BMI is a tool that indicates your body size through a ratio of height and weight.

The formula for calculating your pre-pregnancy BMI is:

Your pre-pregnancy weight (in kilograms) divided by the square of your height (in metres)

For example, if you weighed 68kg and you’re 1.7m tall, your BMI calculation would be 68/(1.7 x 1.7) = 23.5

You can use the healthdirect BMI calculator to work out your pre-pregnancy BMI.

BMI before pregnancy

Your pre-pregnancy BMI will indicate your weight category:

  • BMI of less than 18.5 — underweight
  • BMI of 18.5 to 24.9 — in a healthy weight range
  • BMI of 25 to 29.9 — overweight
  • BMI of 30 or over — obese before your pregnancy

Recommended weight gain

How much weight you should gain depends on your weight before pregnancy.

If you were underweight, you should gain:
Total 12.5kg to 18kg
In the 2nd and 3rd trimester 2kg to 2.6kg per month

If you were a healthy weight, you should gain:
Total 11.5kg to 16kg total
In the 2nd and 3rd trimester 1.5kg to 2.3kg per month

If you were overweight, you should gain:
Total 7kg to 11.5kg
In the 2nd and 3rd trimester 1kg to 1.5kg per month

If you were obese, you should gain:
Total 5kg to 9kg
In the 2nd and 3rd trimester 0.8kg to 1.2kg per month

Things to consider

Your BMI does not necessarily indicate your health, or how fat is distributed on your body.

Weight gain recommendations based on your BMI should be used as a guide.

It’s best to speak to a professional about how much weight to gain during pregnancy, such as:

  • your doctor
  • your midwife
  • an obstetrician
  • a dietitian

They can also consider factors that may increase your recommended weight gain such as:

  • if you are having twins or multiples
  • if you have severe nausea or morning sickness

What are the problems with gaining too much weight?

Your weight gain will be monitored throughout your pregnancy through antenatal care. Gaining more weight than is recommended increases your risk of pregnancy complications such as:

Babies that are born to pregnant people who have put on more weight than is recommended are more likely to:

  • be born prematurely and need intensive care
  • develop heart disease, weight problems and diabetes

These risks increase for pregnant people who live with obesity and smoke.

How much more food should I eat?

When gaining weight for your pregnancy, you don’t have to ‘eat for 2’.

During in the first 3 months, you’ll probably find you don’t need to consume too many extra kilojoules.

In the second and third trimesters, you‘ll need to increase your kilojoule intake. While pregnant, you may find it hard to have larger meals. You should be able to get the extra energy you need by having more snacks throughout the day.

You can help put on the right amount of weight by eating a healthy, nutritious diet that includes the 5 foods groups:

  1. fruit
  2. vegetables
  3. wholegrain breads and cereals
  4. legumes, lean meat and fish
  5. dairy products

You should also check that your diet contains the minerals that keep you healthy and that will give your baby a healthy start. These are:

It’s important to try and avoid fast foods and sugary drinks. These often don’t provide many nutrients for you and your baby.

Make sure you know which foods are safe to eat during your pregnancy.

Keeping up your fluid intake is also important — it’s recommended you drink about 2.3L of water each day.

How much should I exercise?

You should also try to get some regular exercise.

Unless your doctor or midwife tells you otherwise, you can start or continue with regular exercise when you’re pregnant.

You should adjust your activity to suit your stage of pregnancy. You can aim to do about 30 minutes of moderate exercise a day. You can also split this into 3 lots of 10-minute sessions.

Suitable exercises during pregnancy include:

  • walking
  • swimming
  • aqua aerobics
  • pregnancy exercise classes

They will help:

  • prevent you from putting on too much weight
  • reduce your risk of gestational diabetes
  • make you fitter so you can cope with labour better
  • create habits to make losing pregnancy weight easier after you give birth

You should avoid exercise that:

  • involves lifting heavy weights
  • raises your body temperature too high

You can read more about how to exercise during pregnancy.

Resources and support

You can also call Pregnancy, Birth and Baby to speak to a maternal child health nurse on 1800 882 436 or video call. Available 7am to midnight (AET), 7 days a week.

Learn more here about the development and quality assurance of healthdirect content.

Last reviewed: February 2023

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