Advice after your nerve block for surgery
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Introduction
Congratulations on your pregnancy. This leaflet outlines specific aspects of pregnancy care for women who are taking low molecular Weight heparin (LMWH) injections.
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.
Anaesthetic interventions during childbirth
There are a range of options for pain relief in labour, one of which is epidural analgesia. A needle is used to insert a thin tube into the back near the nerves that supply the lower half of the body. Infusion of a local anaesthetic mixture through the tube near the nerves reduces sensation from the lower half of the body thus making labour pains more manageable.
If a woman requires an urgent caesarean delivery or instrumental delivery (where an obstetrician uses forceps or a suction cup to help deliver the baby), a well-working epidural can be topped up with a stronger mixture of local anaesthetic to make the lower half of the body numb. Alternatively, a spinal anaesthetic may be given which is similar to an epidural but is a one-off injection. Again, the lower half of the body is made numb.
Impact of Low Molecular Weight Heparin on safety of epidural analgesia or spinal anaesthesia
Low molecular weight heparins (such as dalteparin) help to “thin the blood” and so are prescribed for pregnant women who are at risk of forming blood clots in the lungs or legs. However, they also reduce the ability of the blood to form clots normally after injury. Occasionally, small blood vessels are punctured in the process of inserting a spinal or epidural. Usually this does not matter as the blood forms a small clot to prevent ongoing bleeding. In women who have recently had a LMWH injection, this does not happen effectively, and excess bleeding may put pressure on the nearby
nerves causing damage. Therefore, if you have had a LMWH injection recently, it may not be possible to have an epidural or a spinal.
- If you are taking a low (preventative/prophylactic) dose of LMWH you would not be able to have an epidural in labour or a spinal anaesthetic within 12 hours of your LMWH injection.
- If taking a higher (treatment) dose you would not be able to have an epidural in labour or a spinal anaesthetic within 24 hours of your LMWH injection.
Alternatives for women who are unable to have an epidural for labour or spinal anaesthesia
All other forms of pain relief in labour are appropriate for use by women who have recently had a LMWH injection. These include Entonox (gas and air) and pethidine injections. For women who require stronger pain relief, a remifentanil PCA (patient controlled analgesia) may be recommended by the anaesthetist on duty. However, you cannot have this within 4 hours of having pethidine. Please see “Remifentanil PCA” information leaflet for more information – ask your midwife if you have not been given a copy.
If a woman requires a caesarean delivery or instrumental delivery urgently and has administered a LMWH injection too recently for them to have a spinal anaesthetic, a general anaesthetic will be given instead. If a woman is due to have an elective caesarean, advice will be given about timing of administration of the last LMWH injection before delivery to ensure spinal anaesthesia can be used.
What to do if you think you are in labour
If you feel what you think is the onset of labour, please notify the triage midwife that you take LMWH injections so that they can advise you about whether you should take your next dose when it is due. If you are being admitted to hospital and are thought to be in labour, do not take your next dose until you are advised to do so.
Summary
- Low molecular weight heparin (e.g. dalteparin) is prescribed for some women in pregnancy who are at risk of blood clots in the lungs or legs.
- Recent LMWH administration makes having a spinal anaesthetic or epidural for labour less safe, as puncture of tiny blood vessels may cause bleeding which can put pressure on nearby nerves.
- Alternatives for women unable to have an epidural for labour due to recent LMWH administration include Entonox, pethidine injections, and remifentanil PCA.
- If a woman is unable to have a spinal anaesthetic due to recent LMWH injection, a general anaesthetic will be used instead.
- If you have any further questions regarding this leaflet, please speak to your midwife or obstetrician.
- Please see https://www.labourpains.org and click on the “leaflets” tab for more information about the issues discussed in this leaflet https://
www. labourpains.org/ translated-information/ english
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/071
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.