Pregnancy & weight

Last updated 29 February 2016 — Last reviewed 01 March 2014

Managing your weight while you are pregnant is not always easy. Knowing how much weight gain and what you can do to keep active is helpful. Hypertension, pre-eclampsia, gestational diabetes, and the need for an induced birth are all risks of gaining too much weight or being overweight in pregnancy, but there are many things you can do to help.

Weight gain in pregnancy

You need to be aware of your weight and what is a healthy weight gain during pregnancy.

Bathroom scales

Weight control while pregnant is not about dieting and weight loss. Some women may lose weight early on because of morning sickness and nausea but there should always be a gradual weight gain in pregnancy.

Often women feel unsure about how much weight they should gain in pregnancy and at what rate. Many women end up gaining too much weight during pregnancy. This puts them at risk of coming of not getting back to their pre-pregnancy weight, which increases their risk of short and long-term health problems.

How much weight gain is too much?

There are no specific guidelines for healthy weight gain in pregnancy in Australia. The average weight gain is 11.5-16kg in women who are in the healthy weight range before they become pregnant.

There are some important messages to think about, including:

  • if you are overweight – i.e. Body Mass Index (BMI) greater than 25 – before you get pregnant then you shouldn’t gain as much weight as a woman who was underweight (BMI less than 20) before pregnancy
  • the ideal weight gain for you during pregnancy should be discussed with your doctor before weeks 12-14 of your pregnancy
  • weight gain should be monitored throughout your pregnancy
  • excessive weight gain (usually more than 16kg) may increase your risk of complications

There are also risks to your baby with excessive weight gain in pregnancy such as:

  • babies born to overweight mothers are more likely than those born to healthy weight mothers to become obese children and adults and to have more health problems
  • women who are obese and smoke are more than twice as likely as healthy weight women to have a baby with congenital (present from before birth) heart disease
  • an increased likelihood your baby will require neonatal intensive care (your baby needs to go to intensive care), perhaps because of prematurity

Managing weight gain

Some simple things to help you curb your weight gain are:

  • regular moderate exercise
  • following the dietary guidelines and including plenty of fresh fruit and vegetables, wholegrain breads and cereals, legumes, lean meat, fish and low fat dairy products
  • reducing your intake of foods and drinks that are high in fat and/or sugar and usually don’t provide many vitamins and minerals

Exercise & physical activity

Sometimes a greater than expected weight gain and accompanying tiredness causes women to reduce or even avoid being active. Sometimes women worry about the effects of exercise on their baby.

There are many benefits to be gained from low impact physical activities such as walking, swimming, aqua-aerobics or specific pregnancy exercise classes including:

  • helping prevent excessive weight gain
  • reduced risk of gestational diabetes
  • enhanced fitness to cope with labour

Unless otherwise advised by your doctor, physical activity can be started or maintained during pregnancy, as long as you adjust your physical activity to suit your stage of pregnancy. Try to include 30 minutes of activity each day.

After the birth of your baby, being active will help to get your body back into shape and help alleviate some of the mental stress of coping with a new baby.

Pregnancy risks if you are overweight

Being overweight increases the risk of pregnancy complications and health problems for the baby. 

Risks associated with being overweight in pregnancy include:

Risk factor Definition Risk for overweight women
Gestational hypertension High blood pressure that develops with pregnancy. Gestational hypertension is more common in women who are overweight.
Pre-eclampsia Increase in blood pressure with fluid retention and protein in the urine that restricts the flow of blood to the placenta. The risk of pre-eclampsia doubles in overweight women and triples in obese women.
Gestational diabetes A form of diabetes diagnosed when higher than normal blood glucose levels first appear during pregnancy. Overweight women have twice the risk of gestational diabetes and obese women eight times the risk, compared with women of healthy weight.
Thromboembolic disease Blood clots in the arteries that typically start in the legs and can break loose and travel to the lungs. Thromboembolic disease is more common in women who are overweight.
Infection Including urinary tract and at birth. Women who are obese have a greater than average chance of developing or resisting infections.
Need for induction of labour Bringing on the birth of the baby early. More common among women who are overweight.
Caesarean birth

Birth via a Caesarean section operation.

Women who are obese have a greater than average chance of requiring Caesarean deliveries.
Stillbirth A baby may have died during pregnancy, labour or at birth. A woman with a BMI of 30 or more is 2.3 times more likely to lose her baby pre-birth and has nearly twice the risk that her baby will die than a woman of healthy weight.
Congenital abnormality Defect present from before birth There is a higher risk of birth defects for the babies of overweight women
Neonatal intensive care For newborn babies who are premature or ill There is a higher risk the babies of overweight women will need neonatal intensive care

What can you do?

  • Learn more about healthy eating
  • Learn more about physical activity and strategies to be more active
  • Consult your doctor and consider referral to a dietitian and/or exercise physiologist

This web page is designed to be informative and educational. It is not intended to provide specific medical advice or replace advice from your health practitioner. The information above is based on current medical knowledge, evidence and practice as at March 2014.

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