Information for women taking Low Molecular Weight Heparin (LMWH) to prevent Venous Thrombo Embolism (VTE)
What is Low Molecular Weight Heparin (LMWH)
What is heparin? Heparin is a blood-thinning treatment that does not harm your baby. When you cut yourself, you bleed. After a while, the blood starts to clot and you stop bleeding. The cut has triggered the clotting cascade, a set of reactions in your blood that leads to clotting to stop the bleeding. Heparin blocks the clotting cascade and so makes it more difficult to clot (thins your blood).
What is low molecular weight heparin?
This is an injection with medication that thins your blood e.g Tinzaparin/Clexane/Dalteparin. LMWH does not need monitoring and does not cross the placenta to your baby.
You give yourself daily injections of LMWH, using pre-filled syringes.
What are the side-effects?
If you follow the instructions above about injecting heparin, you should not have much bruising.
- About 1 out of 56 people (1.8%) develop a skin allergy to heparin.
- Prolonged use of heparin tends to cause osteoporosis (thinning of your bones) and fractures. The risk is very slight in women on LMWH just during pregnancy, with fractures occurring in only about 1 out of 2,500 women (0.04%).
- Heparin causes significant bleeding during pregnancy or delivery in fewer than 1 out of 50 women (2%).
- There is one very are serious reaction to treatment, Heparin Induced Thrombocytopenia (HIT), where blood platelet levels fall sharply, generally in the first two weeks of treatment. Untreated HIT would cause severe clotting which could be fatal. However, a study of almost 3,000 women on LWMH only during pregnancy found nobody developed HIT, so monitoring is not advised unless you have previously had unfractionated heparin.
Nevertheless, if you get a skin reaction other than bruising at the injection site, or your arms or legs become swollen, painful or weak, let your doctor know as soon as possible and mention that you are on low molecular weight heparin.
Instructions for daily injections of LMWH:
It is important to note – if the dose you have been told to have is less than the amount in the syringe, you will need to get rid of the extra before your injection. To do this, hold the syringe vertically with the needle pointing upwards and gently remove the excess by pressing the plunger into the syringe.
- Lie down.
- Gently pinch a large fold of skin on your tummy (or the outside of your thigh, if you prefer) into a fold between your thumb and forefinger. Hold the fold like this while you are injecting.
- Inject straight down into this skin fold, not at an angle.
- Do not try to push out any air in the syringe before injecting yourself – the pre-filled syringe is ready to use immediately.
- Please be aware that heparin tends to thin your blood and may also give you some bruising.
- If you get a skin reaction (not just bruising) where you inject, or your arms or legs become swollen, painful or weak, let your doctor know as soon as possible and mention you are on heparin.
- The recommendation is to stop taking the medication at the onset of labour
- Take the last dose of prophylactic dose LMWH the day before; this should be at least 12 hours before the time planned for caesarean section.
Where can I get more information?
Contact details
You can contact the Antenatal Clinic – see below.
- Bedford Hospital – 01234 792052
- Luton and Dunstable University Hospital – 01582 497430