Haematology 

 

What is low molecular weight heparin (LMWH)?

Low molecular weight heparin (LMWH) (a type of medicine called an anticoagulant) which is used to treat blood clots or reduce the risk of them occurring. In some situations it can be used to try to reduce the risk of miscarriage.

LMWH must be prescribed by a doctor and is always given by injection into the fatty layer underneath the skin (subcutaneous layer). It is usually given once or sometimes twice a day.

Why do we give LMWH in pregnancy and after birth?

During pregnancy the risk of blood clots is increased due to the normal changes occurring in the blood to prepare the body for childbirth. This causes the blood to become more “sticky”. Following the birth of the baby, the risks remain high as the mother’s body takes a few weeks to adapt to not being pregnant. It is important to continue LMWH treatment during this time, and some women will be started on LMWH just to cover the period after the birth.

LMWH is given to women who are thought to have a higher chance of clots during this

time because of their history, or the results of blood tests. Some women will be given

LMWH as part of their treatment because of previous miscarriages or certain

pregnancy complications.

When is LMWH given?

LMWH treatment may be given during pregnancy and / or for between one and six weeks after the birth of the baby, when the risk of clots is highest. It is preferable to give medication for the least time possible, to reduce the risk of side effects.

Are there any risks linked with LMWH treatment?

LMWH is safe to use in pregnancy as it does not cross the placenta and does not affect

the baby. 

The most common side effect for the mother is a small amount of bruising at the injection site. The risk of bleeding with low dose LMWH, due to the “thinning” of the blood, is small. LMWH doesn’t usually cause bleeding by itself, but bleeding caused by other things, for example from a threatened miscarriage, may be a little heavier than normal.

Women are usually advised to stop taking their LMWH when they start in labour or leave out the dose on the morning of a planned delivery. 

An epidural or spinal anaesthetic cannot be given within 12 hours of a dose of LMWH

(24 hours for twice a day injections). LMWH will usually be started again at least four

to six hours after delivery.

The old type of heparin (sometimes referred to as unfractionated heparin) could

sometimes cause osteoporosis (thinning of the bones). This is much less likely with

LMWH, but it is advisable to have plenty of calcium in your diet (for example from milk,

cheese, and yoghurt). 

Around 5% of women experience a skin rash at the site of the injection. If this happens, or if there is any unexplained bruising or bleeding, please contact the hospital on the number on the back of this leaflet.

If a woman has an allergy to one type of LMWH there are other brands of injection which can be used instead.

How do you give LMWH?

The syringes come ready prepared with the correct dose for you to give. You will be shown how to give your own injections, and most women, or their partners, manage this very

easily. The needle on the syringe is very fine, and although the injection may sting slightly, it is not usually too painful. You will be given a sharps box (a strong plastic box just for syringes) so that you can dispose of the syringes safely.

Instructions

  • Make sure you have a sharps box and cotton wool ball ready for after the injection.
  • Wash your hands before giving the injection.
  • Sit in a comfortable position so that you are relaxed.
  • Select the site for injection.

Suitable injection sites include the sides of your tummy (avoiding the area near your belly button) and the front of your thighs. Avoid bruised, scarred, reddened or hard areas.

Rotate the sites to avoid skin irritation. You should never inject into your arms as it is more painful and less effective.

  • Take the syringe and with your thumb and forefinger carefully remove the plastic

sheath covering the needle. Take care not to touch the sterile needle.

  • Do not remove the air bubble in the pre-filled syringe. Hold the syringe halfway

down the barrel in one hand.

  • Use your other hand to gently grasp a fold of skin for your injection. Hold the skin

between your thumb and index finger.

  • Hold the syringe at a right angle to the skin, like a dart. Quickly insert the needle all

the way into the skin fold.

  • Push the syringe plunger down steadily.
  • Keep pushing until all of the fluid is injected into the skin.
  • Make sure you hold the skin fold throughout the injection.
  • Release the skin fold and pull the needle straight out at the same angle that it was

inserted.

  • Place cotton wool over the injection site and apply constant pressure for two to

three minutes.  

  • You may find that the area stings afterwards - this is normal.
  • To avoid bruising do not rub the injection site after you have injected

yourself.

  • Discard the needle in the sharps container and store out of reach of children.
  • When the container is full to the line, close and lock it and give to your GP,

nurse, midwife or the hospital for disposal.

  • Do not put it in the household rubbish.
  • If you forget to take a dose and are close to your next scheduled dose, skip the

missed dose and inject the next dose at the regularly scheduled time. Do not take

a double dose.

  • You should ask your family doctor (GP) to prescribe any further supplies of

Fragmin. (If your GP is unwilling to do this, please let us know). 

  • Your chemist will need at least 24 hours to order the LMWH for you. Please order

in plenty of time to avoid running out.

  • To monitor the dose of your LMWH, we may need to do a blood test. The blood test

must be done four hours after you have taken your injection.

How should LMWH be stored?

It does not need to be kept refrigerated. Store the syringes at room temperature (between 15 and 30ºC). It is important to keep the stock of injections and sharps box in a safe place, out of reach of children. You should ask for a new sharps box before the old one is completely full. Used sharps boxes should be closed and locked and returned to your GP, nurse, midwife or the hospital for disposal. Do not put it in the household rubbish.

Important

Tell a nurse or doctor if you notice any of the following side effects:

  • Red spots under the skin which do not go away when you put pressure on them.
  • You bruise more easily than usual.
  • Your injection sites become red and itchy.

Medication

Do not take any drugs other than those prescribed by your doctor while you are

taking LMWH.

If you need to consult with another doctor or see your dentist, be sure to tell them that you are being treated with LMWH.

 

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Further information

For further information please contact below

 

Haematology Liverpool

Contact Details: 0151 706 3397

Text phone number:  18001 0151 706 3397

 

Author: Haematology Liverpool

Review date: April 2029

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