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High Body Mass Index (BMI) and c-section
Body Mass Index
What are the c-section risks?
Diet and exercise
More help and support
High Body Mass Index (BMI) and c-section
If you had a high Body Mass Index (BMI) before or at the start of pregnancy you are more likely to need a c-section, but you won’t be given one based on BMI alone.
If you are offered a c-section your doctor will tell you their reasons for suggesting the procedure so that you can decide if this is the best option for you and your baby.
You may decide to have a planned c-section if your healthcare team think it is the safest option for you and your baby. This will depend on your wishes as well as your general health and whether you had any problems during pregnancy.
Body Mass Index
Your BMI is a measure that uses your height and weight to work out if your weight is in a healthy range for your height. For pregnant women your BMI calculation will be based on your weight before or at the start of pregnancy.
BMI is not a perfect way to measure your weight. This is because it measures whether someone is carrying too much weight, rather than too much fat. For instance, people who are very muscular may have a high BMI without much fat.
However, for most people, BMI is still a useful way of measuring their weight range.
BMI ranges
For adults of White heritage, if your BMI is:
- Less than 18.5 = underweight range
- 18.5 to 24.9 = healthy weight range
- 25 to 29.9 = overweight range
- 30 to 39.9 = obese range
- 40 or above = severely obese range.
The BMI healthy weight range is different for different ethnicities.
People with Asian, Middle Eastern, Black African, or African-Caribbean family background have a higher risk of developing long-term conditions, such as type 2 diabetes, with a lower BMI.
Because of this, people with these origins should use a different threshold to measure BMI.
If you are from one of these backgrounds, if your BMI is:
- less than 18.5 = underweight range
- 18.5 to 22.9 = healthy weight range
- 23 to 27.4 = overweight range
- 27.5 or above = obese range.
These ranges may mean that people from these ethnic backgrounds get help with their weight earlier than people from White backgrounds.
Your midwife or doctor may use the words ‘overweight’ or ‘obese’ to describe your weight. Many people don’t like these descriptions but your healthcare team will only use them to make sure you get the right care. Nobody will judge you or your weight.
What are the c-section risks?
Most women and birthing people who are overweight have a straightforward pregnancy and birth and have healthy babies. However, being overweight or obese does increase the risk of complications to both you and your baby. You and your healthcare professionals can work together to reduce some of these risks.
Having a high BMI does not always mean you will need a c-section, but you are more likely to have one.
If you have a high BMI, particularly if it’s 40 or more, you’re more likely to have problems during and after a c-section. These include:
- your c-section wound getting infected – your doctor will give you antibiotics during your c-section to lower this risk
- problems caused by the anaesthetic if you have night-time breathing problems (sleep apnoea) – the team will monitor you closely for 12 hours after your c-section
- blood clots - if you have a BMI of 40 or above, you may be offered blood-thinning injections (low-molecular-weight heparin treatment) for at least 10 days after the birth of your baby; it may be necessary to continue taking this for 6 weeks.
You’re likely to see a consultant obstetrician at least once during your pregnancy. This is the most senior doctor who specialises in care during pregnancy, labour and after birth. They will work with you and the rest of your healthcare team to plan your antenatal care and the type of birth you would like.
The best way to protect your and your baby’s health is to go to all your antenatal appointments. This is so your midwife, doctor and any other health professionals can help with any problems you might face and take steps to prevent or manage them.
Find out how you can stay healthy during pregnancy and birth.
Diet and exercise
A healthy diet and being physically active will benefit both you and your baby during pregnancy. It will also help you to have a healthy weight after giving birth. Your midwife, health visitor or GP can support you to keep active and follow a healthy diet.
Find out what exercise you can do safely during pregnancy.
Do not try to lose weight during your pregnancy. It will not reduce the chance of complications and may not be safe.
Keeping active after your c-section will help you recover physically and mentally. Going for gentle walks with your baby is a good way of keeping active while you’re recovering from your c-section.
After your 6-8 week postnatal check, if you don’t have any pain or discomfort, you can exercise. This includes brisk walks or swimming, pilates, yoga, gentle jogging and low resistance gym work.
Listen to your body and avoid pushing yourself too hard while you’re recovering from the surgery.
If your BMI is 30 or more, losing weight before your next pregnancy will improve your chance of having a vaginal birth after a previous c-section (VBAC) if that is something you would like to do in the future.
More help and support
Overweight and pregnant
How much weight should I gain in pregnancy?
Weight management FAQs
It can feel overwhelming when you’re starting new exercise and diet habits. It might help to focus on just changing 1 or 2 things at first. Once you’ve got into a routine then you can work on slowly adding in more changes.
The Tommy's Midwives' Helpline is a free-phone line open 9-5, Monday to Friday for anyone who needs advice, reassurance or support on any pregnancy or planning for pregnancy issue, including mental health.
The number is 0800 0147 800.
The midwives will also answer your questions by email on [email protected].
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