Ghazala Yousuf | Dietitian | The Portland Hospital 

A recent UK wide survey carried out by Royal College of Midwives and the website mumsnet found that many women fail to get proper advice on weight management during and after pregnancy. Almost 63 % were not given any information relating to obesity and almost half of the women surveyed were worried about their weight during pregnancy.

The advice from the National Institute for Health and Clinical Excellence (NICE), published in 2010, advises women to aim to reach a healthy weight before conceiving although recommends ‘Dieting during pregnancy may harm the health of the unborn child.’ and suggests that women are only weighed at their first pregnancy antenatal check-up appointment.

However, a recent review widely commented on in the media and published in the British Medical Journal (May 2012) where National Institute of Health Research (NIHR), compared diet, exercise or a combination of the two factors in pregnancy. While each approach reduced a woman’s weight gain, diet had the greatest effect with an average reduction of nearly 4kg (8.8lbs). This study showed that by carefully advising women on weight management methods, we could reduce weight gain during pregnancy without any reduction in babies’ birth weight. However the evidence from this study alone is not thought to be strong enough to reassess the above NICE guidelines. Results from further ongoing trials are studies are yet to be concluded.

So what is acceptable weight gain in pregnancy?

First and foremost, it is important to accept that you are going to put on weight during pregnancy and by the time you come to give birth, you may on average weigh 12.5 kg more then you did before the pregnancy. Just over a third of your extra weight will come from your baby, the placenta and the amniotic fluid. Here are some averages on how much they weigh each:

-  At birth – a baby weighs about 3.3kg.
-  The placenta – which keeps your baby nourished, weighs 0.7kg.
-  The amniotic fluid – which supports and cushions your baby, weighs 0.8kg

But what about the other two thirds of extra weight? These can be accounted for by the changes that happen to your body while you’re pregnant. Again, the figures are averages only as a guideline: 

-  The muscle layer of your uterus grows and weighs an extra 0.9kg
-  Your blood volume increases and weighs an extra 1.2kg.
-  You have extra fluid in your body weighing about 1.2kg.
-  Your breasts weigh an extra 0.4kg.
-  You’ll store fat, about 4kg, to give you energy for breastfeeding

Remember that this is only an average weight gain and the actual weight gain will depend on your pre-pregnancy weight and BMI.

What is my body mass index and how will it change?

Your body mass index (BMI) measures your weight in relation to your height. It is an accurate way of assessing whether your weight is in a healthy range. The amount of weight you should put on will depend on what your BMI was ‘before’ you became pregnant.

There are no specific recommendations for weight gain in pregnancy in the UK. In the USA these recommendations are based on the mother’s pre-pregnancy weight and height (or their Body Mass Index).

See table below for details:

If you had a high BMI before you conceived you should try to limit the amount of weight you put on during pregnancy, as gaining excessive weight is not good for neither yourself nor your baby’s welfare. It may increase your risk of complications during your pregnancy and during labour; these complications could include high blood pressure, gestational diabetes and pre-eclampsia.

The best thing you can do is to eat sensibly. You’re recommended to have about 2,000 calories a day. You don’t need any more than that until the last three months of your pregnancy, when you’ll need an extra 200 calories a day. You can get the extra 200 calories from, for example, a slice of toast with baked beans or a bowl of wholegrain cereal with semi-skimmed milk.

Instead of dieting, try to follow a healthy well-balanced diet and steer clear of foods high in fat and sugar. A good approach is to go for meals containing carbohydrates with a low glycaemic index. These food types break down more steadily and release energy gradually. Some good healthy suggestions would include:

-  Wholegrain varieties – such as brown rice and pasta, porridge and whole meal bread. Try to ensure that these starchy foods make up a third of what you eat daily. 
-  Fruit and vegetables – at least five portions a day. These should make up another third of what you eat daily. 
-  Low fat dairy – the rest of the diet can be made up of low fat dairy products, such as milk, yoghurt and cheese and proteins, like as meat, fish, eggs and pulses.

Most importantly control the portion sizes remember that you do not need to ‘eat for two!’

If you are concerned about your weight gain in pregnancy and/or have a high BMI at the start of the pregnancy, it may help to see a registered dietitian who can help you to find out how to increase your nutrient intake during pregnancy without loading up on calories.