Advice after your nerve block for surgery
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Introduction
Arriving at labour ward Congratulations on your pregnancy. This leaflet outlines specific anaesthetic aspects of pregnancy care for women who have a high body mass index (BMI).
Who are anaesthetists?
Anaesthetists are doctors who work alongside obstetric doctors and midwives in the care of pregnant women. Anaesthetists provide some forms of pain relief in labour and anaesthesia
for childbirth when required.
Body Mass Index (BMI) and childbirth
BMI is the ratio of weight to height and can be used to determine if a person is underweight, overweight or obese. Research shows that women who have a high BMI are at greater risk of certain complications in pregnancy. For example, women with a BMI of over 35 are about twice as likely to need an instrumental delivery (where the obstetrician delivers the baby with forceps or a suction cup) or caesarean section compared to women whose BMI is within the normal range of 20-25.
A higher BMI can also make some procedures more difficult, such as putting a drip into a vein, or inserting an epidural or spinal anaesthetic. If your BMI is very high (over 50, or over 40 with associated health problems) you may be offered an appointment with an anaesthetist during your pregnancy. This will allow us to discuss and plan anaesthetic and pain-relief choices with you. If your BMI is over 40 but less than 50 with no associated problems, it is recommended that you see an anaesthetist when you arrive in early labour.
Arriving at labour ward
When you have been admitted to labour ward please ask your midwife to inform the anaesthetist on duty that you have arrived. The anaesthetist on duty for labour ward will then assess you and discuss your options for pain relief.
Anaesthetic choices at caesarean section
If you are advised to have a caesarean section, either planned or as an emergency, it is usually best to remain awake by having a spinal anaesthetic (a one-off injection in the lower back) or an epidural anaesthetic (similar to a spinal but a very thin tube is left in the back so that further pain-relieving medication can be given) rather than having a general anaesthetic. This is beneficial for both women and their babies as it allows earlier breast feeding and skin-to-skin contact, facilitates the presence of a partner at delivery, and provides good post-operative pain relief. If your BMI is
raised, it can be more difficult to find the right space in your back to put the spinal or epidural
needle and so these procedures may take longer.
However, giving you a general anaesthetic is likely to be more challenging as well, as having a higher BMI makes the insertion of a breathing tube necessary for a general anaesthetic more difficult. This is an additional reason why it is safer for a woman with a high BMI to have an epidural or spinal anaesthetic for a caesarean.
Epidurals in labour
We recommend that women with a high BMI consider having an epidural in labour because
of the increased risk of needing help with delivery – a well-working epidural that has
been put in to help manage labour pain can be topped up with stronger medicine to make the
bottom half of the body numb for the purposes of an urgent caesarean or instrumental
delivery. This may reduce the need for trying to insert a spinal anaesthetic in a hurry, and
therefore possibly avoiding the need for a general anaesthetic if attempts at a spinal
anaesthetic were to be unsuccessful. If you do decide to have an epidural, it is advisable to
have it early in labour – high BMI together with difficulty staying still associated with the pain of the latter stages of labour make it more challenging to insert an epidural. If we were unable to put in an epidural (either because it was too difficult or because you are taking blood thinning injections), there are other methods of pain relief that you may be offered such as a remifentanil PCA (see “Remifentanil PCA” information leaflet – ask your midwife if you have not been given a copy).
Reducing acid in your stomach and avoiding eating in labour
You are advised not to eat and will be offered antacid tablets in labour to reduce the contents and acidity in your stomach. This minimises the risk of acidic stomach contents coming up into the throat and then down into the lungs at the time of a general anaesthetic, if this becomes necessary. You can freely drink water, non-fizzy sports drinks or other clear fluids.
Blood thinning medications
If you are taking blood thinning injections (such as dalteparin injections) please tell your midwife as this can have implications for the timing of epidural or spinal injections.
Summary
- Some pregnancy-related complications are more common in women with a high BMI.
- When you are admitted in labour, remind your midwife that you need to see an anaesthetist.
- It can take longer and be more difficult to put in an epidural or spinal and so it may be better to have an epidural earlier in labour to maximise our chances of success, and in case your baby needs to be delivered by caesarean or instrumental delivery in an emergency.
- It is generally better for you to stay awake during a caesarean delivery (with a spinal or epidural anaesthetic).
- Speak to your midwife or obstetrician if you have any questions about this leaflet.
If you require further information or advice, then please contact the anaesthetic department at the hospital you were treated at:
Frimley Park Hospital – 0300 613 4161
Wexham Park & Heatherwood Hospitals – 0300 615 3195
Contact us
If you have any queries relating to this information, please contact the Anaesthetics service.
About this information
Service:
Anaesthetics
Reference:
B/073
Approval date:
10 January 2025
Review date:
10 January 2028
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Important note
This page provides general information only. It is developed by clinical staff and is reviewed regularly every 3 years for accuracy. For personal advice about your health, or if you have any concerns, please speak to your doctor.