Obesity, which is usually defined as having a body mass index (BMI) of more than 30, is increasingly common. Around 15-20% of pregnant women are now obese. Before you get pregnant you can use the BMI healthy weight calculator to work out your BMI. But once you're pregnant this may not be accurate, so consult your midwife or doctor instead.
Risks to you and your baby
Obesity can cause problems both with becoming pregnant and during pregnancy. If you're overweight, you may have difficulty conceiving, and if you're having fertility treatment, it may not be as effective.
In pregnancy, a BMI of more than 30 increases the risk of a range of health problems for you and your baby.
More than half of women who die during pregnancy are overweight or obese. Obesity raises the risk of the following conditions in pregnant women:
Most pregnancies of obese women are successful, but problems for your baby can include:
There's also evidence that babies born of obese mothers are more prone to health problems later in life, including obesity and diabetes.
What you can do
The best way to protect your health and your baby’s wellbeing is to lose weight before you become pregnant. By reaching a healthy weight, you increase your chances of conceiving naturally and cut your risk of all the problems associated with obesity in pregnancy. Contact your GP for advice on how to lose weight. Your doctor may be able to refer you to a specialist weight-loss clinic.
As yet, there's no evidence to suggest that losing weight during pregnancy will lower your risks, but eating healthily (including knowing what foods to avoid) and doing activities such as walking and swimming is good for all pregnant women. If you weren’t active before pregnancy, always consult your midwife or doctor before starting a new exercise regime when you're pregnant.
If you become pregnant before losing weight, you'll be tested for gestational diabetes. You may also be referred to an anaesthetist to discuss issues such as having an epidural during labour. You're more likely to need this type of pain relief (because obese women are more likely to have an instrumental (ventouse or forceps) delivery), and it can be difficult for the epidural to be given.
If you're obese, discuss your birth options with your midwife or doctor, because there are restrictions on which women can safely deliver at home or in a birthing pool. Because overweight women are more likely to need an instrumental birth, it's usually safer to opt for a hospital birth where there's faster access to medical care and pain relief options, if needed.
Find out more about your options on where to give birth.
The National Institute for Health and Clinical Excellence (NICE) has produced guidelines on weight management before, during and after pregnancy (PDF, 68kb). It is not aimed at women who have a BMI over 30, but it has useful information on achieving, and maintaining, a healthy weight.
