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Why it’s a bad idea to eat for two during pregnancy

You can achieve a healthy weight gain during pregnancy by eating healthily and being physically active. TuttleTree

In the past, women have often been told they should eat for two during pregnancy. This old adage is not true anymore, especially if women are overweight or obese when starting their pregnancy.

Restricting weight gain during pregnancy is important for overweight and obese women to improve their health and give their baby the best start to life.

Australians’ bodyweight has grown steadily over the past few years with 25% of children (five to 17 years) and 61% of adults now overweight or obese. These rates put us squarely in the ‘worst’ third of international obesity levels.

This excess weight has an enormous impact on our rates of diabetes, heart disease and other disorders, and it may even reduce our life expectancy.

Obesity is most commonly measured using the body mass index (BMI). BMI is a weight-to-height ratio, and is considered to be a reasonable reflection of body fat for most people. BMI is calculated by dividing body weight in kilograms by the square of height in metres (kg/m).

For example, a woman who is weighs 70 kg and whose height is 1.75 metres will have a BMI of 22.9. There are a number of BMI calculators available on the internet which make calculating BMI easy.

A ‘normal’ BMI is classified as being from 20–25kg/m2, ‘overweight’ is having a BMI 25.01–30kg/m2 and ‘obese’ is a BMI of more than 30kg/m2.2

Obesity in pregnancy is a common problem. Australian research conducted in Brisbane showed 34% of pregnant women attending a major maternity hospital were overweight, obese or morbidly obese.

Risks of overweight and obesity

Obesity in pregnancy is associated with a number of problems and complications, both for the mother and her baby.

Pregnant women who are obese at the onset of pregnancy have a higher chance of having a number of problems in their pregnancy and while giving birth. This includes having pregnancy-related diabetes (gestational diabetes), increased blood pressure (hypertension), and problems with clots in the legs or the lungs.

These women also have more back and pelvic pain and problems with urinary incontinence (not being able to control passing urine). Studies have shown that the chance of having a stillbirth is higher in overweight and obese women than women who have a normal BMI.

Women who are obese during pregnancy are more likely to have their labour induced, and as women’s BMI increases so does the chance of having a caesarean section or complications during the birth.

After the baby is born there is also a higher chance of bleeding (postpartum haemorrhage) and infections. Women who are obese may also have more difficulties with starting breastfeeding.

There are also risks for the baby. Babies born to mothers who are obese are more likely to need to be admitted to a neonatal intensive care unit with complications and seem to have higher rates of breathing and other problems.

Obese women may also have less choice about where and how they give birth. There may be restrictions on which hospital they can attend and whether they can access a birth centre or homebirth. There may also be restrictions on the use of birthing pools and types of pain relief that can be given.

Healthy weight gain

The recent increase in obesity in Australia and other countries has made midwives, doctors and other health professionals think carefully about how much weight women should gain in pregnancy. Unfortunately at the moment there are no formal, evidence-based guidelines from the Australian government or professional bodies on what is the best weight gain during pregnancy.

The Institute of Medicine guidelines from the United States are widely used to give women and care providers advice about weight gain in pregnancy. These state that healthy women who have a BMI in the normal range should gain 11.5 to 16 kg during pregnancy, whereas overweight women (BMI 25–29.9) should gain seven to 11.5 kg and obese women (BMI greater than 30) should only put on five to nine kilograms.

US research suggests that women who gain weight within these ranges are more likely to have better maternal and infant outcomes than those who gain more or less weight.

Excessive weight gain during pregnancy often means that it is harder to lose weight after the baby is born. Women tend to go into their next pregnancy a bit heavier than their last and this gradual increase can lead to long-term health problems.

Research has shown that modest amounts of weight loss between pregnancies can reduce the risk of complications like gestational diabetes in the next pregnancy. Therefore, it is really worthwhile trying to lose weight through a healthy diet and exercise after the baby is born.

You can achieve a healthy weight gain in pregnancy by eating healthily and being physically active. There is no need to “eat for two” or drink full fat milk. If you feel hungrier, some extra serves of fruit and vegetables and healthy snacks should be enough. Moderate physical activity will not harm you if you are pregnant, nor will it harm your unborn baby.

Gradual weight loss after the baby is born and moderate-intensity physical activity will not affect your breastfeeding or the quality of your breast milk.

The weigh-in

Weighing women in pregnancy used to be commonplace 20 or 30 years ago but this has gone out of fashion in the last decade. Weight gain was originally recorded because there were concerns about women not putting on enough weight.

We stopped weighing women because it was thought it was making them more anxious and adding unnecessarily to their list of concerns. It was also found that weighing women at each pregnancy visit was not a useful way of assessing how well the pregnancy was going or how well the baby was growing.

Measuring weight in pregnancy is coming back into the practice of many midwives and doctors because of the concerns about the effects of obesity on pregnancy and babies. It is particularly important that women are weighed and their height measured early in pregnancy so that her BMI can be measured and advice provided about the right amount of weight to gain.

After their initial weigh-in, most women will not be weighed again through their pregnancy. Some midwives and doctors are weighing women at each pregnancy visit but this is not a general recommendation. Being weighed through pregnancy may be an opportunity to talk about weight gain as well as diet and exercise.

Talking about weight at any time is difficult. Many people are self conscious about their weight and often embarrassed to talk about it, especially if they are obese and know that there are problems associated with their weight.

Midwives and doctors also find it difficult to talk with pregnant women about their weight. Sometimes this is because they do not want to upset the woman or put more pressure on her to lose weight. Or they might even feel that they cannot alter a woman’s weight gain while they are pregnant so they will not bring it up.

Being overweight and obese in pregnancy can mean that you will be at risk of complications and problems during pregnancy, labor and birth and the postnatal period. Thinking about your weight during pregnancy and trying to keep healthy by eating well and being active are the most important things you can do.

Talk to your midwife or doctor about your weight in pregnancy. They will be able to provide good advice about making sure you are as healthy as possible and can start motherhood in the best way possible.


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  2. WHO. BMI classification Geneva: World Health Organization, 2011.
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