Skip Ribbon Commands
Skip to main content

Being Overweight in Pregnancy

Being Overweight in Pregnancy - What is it for

Most women who are overweight have a straightforward pregnancy and labour, giving birth to healthy babies. However, being overweight or obese does increase the risk of complications to both you and your baby. The higher your BMI, the greater the risks. This brochure provides information that will help you understand more about the risks and what to look out for to help you achieve a healthy pregnancy.

What is BMI?
BMI is body mass index, which is a measure of your weight in relation to your height. A healthy BMI is in the range of 18.5 to 24.9. A person with a BMI in the range of 25 to 29.9 is considered overweight. A person with a BMI of 30 or above is considered to be obese.

You can calculate your BMI by using the calculator on the HealthHub website: programmes/93/bmi-calculator

If your BMI at your first antenatal booking visit is 35 or above, you may be offered antenatal care in the clinic which specialises in taking care of patients with high BMI.

What are the risks of high BMI in pregnancy?
Some of the pregnancy complications more commonly seen in patients who are overweight or obese include:

Thrombosis occurs when blood clot forms in your legs (venous thrombosis) or in your lungs (pulmonary embolism), which can be life-threatening. Pregnancy itself increases your risk of developing thrombosis. If you are overweight, the risk of developing thrombosis is further increased. Your risk for thrombosis will be assessed at your first antenatal visit and will be monitored during your pregnancy and after childbirth. You may be offered injections of a medication called low-molecular-weight heparin to reduce your risk of thrombosis if deemed high risk. This is safe for you and your baby.

Gestational diabetes
Gestational diabetes (GDM) can develop during pregnancy and the risk of GDM is three times more likely to develop if your BMI is 30 or above. You will be offered a test for gestational diabetes between 24 and 28 weeks, earlier if you have other risk factors. If the test shows that you have GDM, you will be referred to the Obstetric Day Assessment Centre (ODAC) for education, further testing and treatment as required.

High blood pressure and pre-eclampsia
Being overweight increases your risk of developing high blood pressure and pre-eclampsia. If you have a BMI of 30 or above, your risk of pre-eclampsia is 2 to 4 times higher compared to those with a BMI under 25. Your risk of developing pre-eclampsia may be further increased if:

  • You are over 40 years old
  • You have had pre-eclampsia in a previous pregnancy
  • Your blood pressure was already high before pregnancy If you have these or other risk factors, your doctor may recommend a low dose of aspirin to reduce the risk of you developing pre-eclampsia.


Risks to your baby

  • The overall likelihood of a miscarriage in early pregnancy is 1 in 5 (20%), but if you have a BMI of 30 or above, your risk increases to 1 in 4 (25%).
  • The risk of your baby developing neural tube defects (problem with the development of the baby’s skull and spine) and you having a stillbirth is nearly doubled when your BMI is 30 or above.
  • If you are overweight, you are more likely to have a baby weighing more than 4kg, which increases the risk of complications for you and your baby during birth.


Additional care during your pregnancy
High-dose folic acid
Folic acid helps to reduce the risk of your baby having a neural tube defect. If your BMI is 30 or above, a daily dose of 5mg of folic acid is recommended, ideally, from a month before you conceive and throughout the first trimester (12 weeks) of your pregnancy.

Healthy eating and referral to dietitian
A healthy diet will benefit both you and your baby during pregnancy and after birth. You may be referred to a dietitian to assess your dietary habits and help optimise your meals. The focus will be on maintaining a healthy diet. Trying to lose weight by dieting during pregnancy is not recommended. However, by making healthy changes to your diet, you may not gain any weight during pregnancy and you may even lose a small amount. This is not harmful. The website programmes/191/nutrition-hub/eat-more can provide more information about a healthy diet.

You should stay active and engage in regular exercises during your pregnancy to prevent excessive weight gain. This website provides useful information about physical activity for pregnant women. Some examples of healthy exercise include swimming, walking and pregnancy yoga.

Additional ultrasound scans
An ultrasound scan is routinely arranged at 20 weeks to check for structural problems that your baby may have. If your BMI is raised, this scan may be less accurate at picking up problems. You may also need additional ultrasound scans to check your baby’s development, growth and position throughout your pregnancy as monitoring the baby’s size and position through external palpation of the abdomen can be less accurate if your BMI is more than 35.

Referral to anaesthetist
All types of pain relief options can be considered for you during labour. However, having an epidural can be more difficult if you are overweight. You will be offered a referral to talk to the anaesthetist in the third trimester about your choice for pain relief during labour and anaesthesia options in case you need a caesarean delivery.

Labour and giving birth
There is an increased risk of complications during labour and birth, particularly if your BMI is 40 or more. These complications include:

  • Your baby being born before 37 weeks of pregnancy (preterm birth)
  • A longer labour
  • Your baby’s shoulder becoming ‘stuck’ during birth (shoulder dystocia)
  • An emergency caesarean section
  • Heavy bleeding, anaesthetic complications and wound infection


Your doctor will be discussing the timing of delivery and birth options (vaginal birth or caesarean section) with you at around 36 weeks of your pregnancy.

After giving birth
After giving birth, some of your health risks may still be present. However, you can minimise the risks in a number of ways, such as:

Prevention of thrombosis

  • Try to be as active as soon as you feel comfortable – avoid sitting still for long periods
  • Wear special compression stockings, if you have been advised you need them
  • If you have a BMI of 40 or above, you may be offered blood-thinning injections after the birth of your baby


Healthy eating, exercise and lose weight
Continue to follow the advice on healthy eating and exercise during your pregnancy. If you want to lose weight once you have had your baby, you can discuss it with your doctor. For some women where lifestyle measures alone have been ineffective, bariatric surgery may be considered.

Family planning and contraception
Plan for when and if you want to get pregnant again. Speak to your doctor about the contraceptive options available for you.

Being Overweight in Pregnancy - Symptoms

Being Overweight in Pregnancy - How to prevent?

Being Overweight in Pregnancy - Causes and Risk Factors

Being Overweight in Pregnancy - Diagnosis

Being Overweight in Pregnancy - Treatments

Being Overweight in Pregnancy - Preparing for surgery

Being Overweight in Pregnancy - Post-surgery care