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A. Thrombosis is a blood clot in a blood vessel (a vein or an artery).
Venous thrombosis occurs in a vein. Veins are the blood vessels that take blood back to the heart and lungs whereas arteries take the blood away.
A. Deep vein thrombosis (DVT) is a blood clot that forms in a deep vein of the leg, calf or pelvis.
A. Pregnancy increases your risk of a DVT, with the highest risk being just after you have had your baby.
However, venous thrombosis is still uncommon in pregnancy or in the first 6 weeks after birth, occurring in only 1–2 in 1000 women.
A DVT can occur at any time during your pregnancy, including the first 3 months.
A. The symptoms of a DVT usually occur in only one leg and can include:
You should seek advice immediately from your doctor if you notice any of these symptoms.
During pregnancy, swelling and discomfort in both legs is common and does not always mean that there is a problem. Ask your doctor if you are worried.
A. Venous thrombosis can be serious because the blood clot may break off and travel in the bloodstream until it gets lodged in another part of the body, such as the lung. This is called a pulmonary embolism (PE) and can be life threatening. However, dying from a PE is very rare in women who are pregnant or who have just had a baby.
The symptoms of a PE can include:
You should seek help immediately if you experience any of these symptoms. Diagnosing and treating a DVT reduces the risk of developing a PE.
A. You are at increased risk of venous thrombosis if any of the following apply to you.
A. The evaluation for DVT/PE during pregnancy is as follows:
DVT
If you are experiencing symptoms, your doctor will examine your leg and may recommend an ultrasound scan of your leg to see whether you have a thrombosis.
If no thrombosis is seen but you are still having symptoms, the ultrasound scan may be repeated a few days later.
PE
The tests may include:
A. The chest X-ray, CT scan and VQ scan all use radiation.
The chest X-ray uses a tiny dose of radiation that is not considered harmful for you or your baby.
The CT and VQ scans both carry a small risk but this needs to be weighed up against the risk to you and your baby of an undiagnosed PE. The risk to your baby of developing childhood cancer after a VQ scan or a CT scan is extremely low although it is slightly higher with a VQ scan than with a CT scan.
However, a CT scan gives a higher dose of radiation to your breasts than a VQ scan and the lifetime risk of breast cancer may be increased. Your doctor will talk to you about the benefits and risks and which test would be best for you.
A. If your doctor suspects that you have a venous thrombosis, you will be advised to start on treatment with an injection of a drug called heparin to thin the blood. There are various types of heparin. The most commonly used in pregnancy is low-molecular-weight heparin (LMWH).
For most women, the benefits of heparin are that it:
A. Heparin is given as an injection under the skin (subcutaneous) at the same time every day (sometimes twice daily).
The dose is worked out for you according to your weight in early pregnancy.
You may not need to stay in hospital for the whole duration of treatment with heparin.
You (or a family member) will be shown how and where in your body to give the injections.
You will have regular check-ups as an outpatient.
A. Low-molecular-weight heparin does not cross the placenta and therefore cannot harm your baby.
There may be some bruising where you inject – this will usually fade in a few days.
One or two women in every 100 (1–2%) will have an allergic reaction. If you notice a rash after injecting, you should inform your doctor so that the type of heparin can be changed.
A. Treatment is usually recommended for the remainder of your pregnancy and for at least 6 weeks after the birth.
The minimum treatment time is 3 months and you may need to continue it for longer.
A. Stay as active as you can.
A. If you think you are going into labour, do not have any more injections.
An epidural injection (a regional anaesthetic injection given into the space around the nerves in your back to numb your lower body) cannot be given until 24 hours after your last heparin injection. You will have the option of alternative pain relief.
If the plan is to induce labour, you should stop your injections 24 hours before the planned date.
A. If you are having a planned caesarean section, your last heparin injection should be 24 hours before the planned delivery. Heparin will usually be restarted within 4 hours of the operation.
If your baby needs to be born by emergency caesarean section within 24 hours of your last injection, you will not be able to have an epidural or spinal injection. Instead, you will need a general anaesthetic for your operation.
A. Treatment should be continued for at least 6 weeks after birth. You are likely to need treatment for longer if your DVT or PE was diagnosed late in pregnancy or after birth.
There is a choice of treatment after birth of continuing with injections of heparin or using warfarin tablets. Your doctor will discuss your options with you.
A. Yes – both heparin and warfarin are safe to take when breastfeeding.