Weight management during pregnancy

Pregnancy is a time when looking after your own health is important because it directly affects the health of your baby.

A healthy diet is very important whilst you are pregnant as it will help to keep you fit and well and help your baby to develop and grow.

If you have a body mass index (BMI) above 30, you should ideally limit your weight gain in pregnancy to between 5-9kg – what is body mass index?

You do not need to go on a special diet but there are foods that all women should avoid in pregnancy.

Despite what you may have heard, you do not need to eat for two but you may find you are more hungry than normal. You may have to change high fat/sugar snacks for healthier options and alter the amounts of different foods you eat.

Weight gain is inevitable during pregnancy and is quite normal! Gaining weight at a steady pace will help your baby grow and develop and reduce the risk of complications during your pregnancy.

Please explore the following sections for more information:

Research has shown that excessive weight gain in pregnant women with a body mass index (BMI) above 30 has been linked to several risks and complications. The higher a woman’s BMI, the higher the risks.

These risks include:

  • miscarriage – the overall risk of miscarriage under 12 weeks is one in five (20%); if you have a BMI over 30, the risk is one in four (25%)
  • gestational diabetes – if your BMI is 30 or above, you are three times more likely to develop gestational diabetes than women whose BMI is below 30
  • high blood pressure and pre-eclampsia– if you have a BMI of 35 or above at the beginning of your pregnancy, your risk of pre-eclampsia is twice that of women who have a BMI under 25
  • blood clots – all pregnant women have a higher risk of blood clots compared to women who are not pregnant, and if your BMI is 30 or more the risk is additionally increased
  • shoulder dystocia – the baby’s shoulder becoming “stuck” and difficult to deliver during labour
  • heavier bleeding than normal after the birth and more chance of infection in wounds
  • having a baby weighing more than 4kg (8lb 14oz) – the overall risk of this for women with a BMI between 20 and 30 is 7 in 100 (7%); if your BMI is over 30, your risk is doubled to 14 in 100 (14%)

When it comes to the delivery of your baby, you are also more likely to need induction, instrumental (ventouse or forceps) delivery, or an emergency caesarean section.

The risks include;

  • being born early (before 37 weeks)
  • an increased risk of stillbirth from an overall risk of 1 in 200 in the UK to 1 in 100 if you have a body mass index (BMI) of 30 or more
  • a higher risk of fetal abnormality, particularly of the heart and spine for example, neural tube defects like spina bifida. Overall, around 1 in 1,000 babies are born with neural tube defects in the UK. If your BMI is over 40, the risk is three times the risk of a woman with a BMI below 30

These problems can also happen to any pregnant woman, whether she is overweight or not.

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