Weight gain in pregnancy

Keeping a healthy weight is important for your overall health and wellbeing. Being underweight or overweight during pregnancy can impact your health and your baby's health.

What is my ideal healthy weight before pregnancy?

Your ideal weight before pregnancy is different for everyone. You can calculate your pre-pregnancy BMI based on your height and weight. A healthy BMI is between 18.5 and 24.9.

You should also remember that BMI does not necessarily indicate your health, or how fat is spread around your body.

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

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.

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

You will gain weight during pregnancy because your baby is growing. Your body is also developing extra body tissue and retaining more fluid. This includes:

• the amniotic fluid around your baby
• the placenta
• an increased amount of blood in your body

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 feel sick at the thought of other foods you used to like. This can also affect your weight gain.

The average person gains between 11.5kg and 16kg of weight during pregnancy. But how much weight you 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 working out your pre-pregnancy body mass index (BMI).

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

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

Weight gain recommendations based on your BMI should only 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 will also consider factors that may affect your recommended weight gain such as:

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

Gaining more weight than is recommended increases your risk of pregnancy complications such as:

• gestational diabetes
• high blood pressure
• pre-eclampsia
• caesarean section
• stillbirth

Babies who are born to people who are living with overweight or obesity, or 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 if you live with obesity or smoke.

Babies who are born to people who have a low pre-pregnancy weight or who gain less weight than recommended during pregnancy are more likely to:

• be born prematurely
• be small and have a low weight when born

You don't have to 'eat for 2', when pregnant.

During the first 3 months, you'll probably find you don't need to eat too many extra kilojoules. Kilojoules measure how much energy you get from food and drinks. Another way to measure food energy is in calories.

In the second and third trimesters, you'll need to increase your kilojoule intake. To be healthy, just eat a bit more vegetables, lean protein and wholegrains every day.

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

• fruit
• vegetables
• wholegrain breads and cereals
• legumes, lean meat and fish
• dairy products

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

• folic acid
• iron
• calcium
• iodine

Foods to avoid

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

Some foods are not safe to eat during pregnancy. Your immune system is lower during pregnancy. This means it harder to fight off illness and infection caused by bacteria found in some foods.

Learn which foods are safe to eat during pregnancy.

• While pregnant, you may find it hard to eat larger meals. Try eating smaller meals and have healthy snacks throughout the day.
• Eating regular meals helps you get enough nutrients and energy.
• Try adding an extra handful of vegetables when cooking.
• Bake or grill food instead of frying it in oil.
• Make a healthy food swap to replace less healthy food with more nutritious food.

Keeping up your fluid intake is also important — it's recommended you drink about 2.3L (10 cups) of water each day. You need a little more water when you are pregnant than when you are not. This is because your body holds onto more fluid, and it is important for your baby and the amniotic fluid that protects your baby.

Unless your doctor or midwife tells you otherwise, you can start or continue with regular exercise when you're pregnant. Staying active can support your overall health and wellbeing.

You should adjust your activity to suit your stage of pregnancy. 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

Exercise will help:

• stop you from putting on too much weight
• lower your chance of gestational diabetes
• make you fitter for labour
• create habits to make losing weight easier after you give birth

You should avoid exercise that:

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

Read more about exercise during pregnancy.

If you are pregnant with twins, read about weight to gain from The Royal Women's Hospital.

Read more about pregnancy and healthy eating from Food Standards Australian and New Zealand.

The National Health and Medical Research Council (NHMRC) has more information on healthy eating during your pregnancy.

Multilingual resources about healthy eating in pregnancy are available from Health Translations.

You can find tips on how to support someone who is pregnant from the Australian Government Department of Health, Disability and Ageing.