If You Have a BMI Over 40

Body Mass Index (BMI) is a measure of your height and weight and indicates if you are overweight. Pregnant women with a BMI over 35 are at higher risk of complications than those with a normal BMI (20-25).

However, with careful planning and discussions with your midwife, obstetrician and anaesthetist these risks can be kept as low as possible. We need your help to do this and we might suggest certain things. 

If your BMI is over 50 we will book you an appointment with a consultant anaesthetic doctor to discuss any concerns you or we might have. We will aim to do this in the final few weeks of your pregnancy before you go into labour.

If your BMI is over 40 but less than 50 an anaesthetic doctor will visit you when you come into Southmead Hospital in labour. If you wish to see an anaesthetist earlier in your pregnancy you are very welcome to ask for an appointment in antenatal clinic and in some cases, your obstetrician may advise an appointment.

Is there anything I need consider?

Women who have a high BMI have as much as twice the risk of needing a Caesarean Section delivery of their baby and this may need to be done as an emergency for the birth of their baby. A high BMI can cause problems when you have a general anaesthetic (go to sleep) for an operation. In most cases it is safer for you to have an epidural or a spinal block if you need a Caesarean Section birth. This means an injection is given into your back to make your lower body numb.

You are awake for the operation and this has many advantages for you and your baby however, making you numb in this way can be difficult if you have a high BMI. It may be harder to find the correct place to put the needle in your back than if your BMI was lower, and sometimes it is more difficult to get the numbness to work straight away.

There are times when we need to deliver your baby as quickly as possible. If you have already had an epidural put in during your labour, and it is working well, we can often use it to give very quick anaesthesia (numbness) for a Caesarean birth, or if we need to deliver your baby using forceps or ventouse (suction cup). This cuts down delays and reduces the chance of you needing to have a general anaesthetic (go to sleep) in an emergency.

For this reason, if your midwife or obstetric doctor feels that your labour is not entirely straightforward, we normally suggest that you should think about having an epidural sooner rather than later in labour. This allows the anaesthetist more time to put it in and to make sure it is working well for you.

Can I eat during labour?

We will give you medication to reduce the acid in your stomach during your labour. We strongly recommend not eating any food or having fizzy drinks when you are in labour. Water and sports isotonic drinks are much safer. We suggest that you bring a couple of bottles with you when you come in to hospital in labour.

What are the risks of blood clots/DVTs?

From the start of pregnancy you have been at a higher risk of getting a blood clot in your legs. Whilst you are moving around your risk is lower but during labour, and in the few days after your baby is born, you may be in bed a lot more.

To reduce the risk of clots we may need to give you:

  • Elasticated stockings
  • Heparin injections once or twice a day to thin your blood for 7 days after the birth. We will teach you and/or your partner how to do this, if appropriate.

For more information visit www.nhs.uk/conditions/pregnancy-and-baby/pages/overweight-pregnant

If You Have a BMI Over 40