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A. 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, so it is important to see your obstetrician early in pregnancy.
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. Your risk of venous thrombosis is increased further if any of the following apply to you.
A. You may be able to reduce your risk, as most DVTs and PEs that occur during pregnancy and after birth are preventable.
You will have a risk assessment during pregnancy and after you have had your baby, during which your obstetrician will ask whether you have any of the risk factors above. This helps to decide whether you would benefit from preventive treatment. This will depend on which risk factors you have and how many.
Some risk factors, such as previous thrombosis, are significant enough on their own for treatment to be recommended.
Other risk factors may not be enough on their own for you to require treatment. Your obstetrician will talk with you about your risk factors and explain why treatment may be advised in your case.
If you are diagnosed with a DVT, your doctor will give you treatment to reduce the risk of a PE occurring.
A. Risk assessment will take place
Before pregnancy
If you have any of the risk factors listed above and are planning a pregnancy you should talk to your obstetrician. You may need to see an obstetrician early in pregnancy to discuss starting treatment.
If you have previously had a DVT or PE or have a thrombophilia you should seek hospital appointment with a doctor who specialises in thrombosis in pregnancy.
If you are already taking warfarin to treat or prevent venous thrombosis, you may be advised to change to heparin injections because warfarin can be harmful to your unborn baby.
Most women are advised to change before becoming pregnant or as early as possible in pregnancy. For some women, warfarin may be the only option. Talk to your doctor before you become pregnant so that any changes can be planned to keep you and your baby as healthy as possible.
During and after pregnancy
Your obstetrician would carry out a risk assessment at your first antenatal booking and at around 28 weeks of pregnancy. A risk assessment should also be carried out if your situation changes during your pregnancy and/or if you are admitted to hospital. After your baby is born a further risk assessment should be done.
A. Yes. Your risk can either increase or decrease.
You may start by having one or two risk factors but your risk can increase if you develop other factors, such as becoming unwell, developing severe varicose veins, travelling for over 4 hours or having a complicated birth. In this case, you may be advised to start taking treatment.
Your risk may also decrease, for example if you stop smoking. Treatment may then no longer be necessary.
A. You can reduce your risk of getting of a DVT or PE:
You may be advised to start treatment with injections of heparin, which is an anticoagulant used to thin the blood.
There are various types of heparin. The most commonly used in pregnancy is low-molecular-weight heparin (LMWH).
Heparin is also used to treat venous thrombosis, but the dose of heparin used to prevent a venous thrombosis is usually less.
For most women, the benefits of heparin are that it reduces the risk of a venous thrombosis or a PE developing.
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 depending on your risk factors and your weight in early pregnancy or before you became pregnant.
You may be on a low-dose or a high-dose regimen. You (or a family member) will be shown how and where in your body to give the injections. You will be given advice on how to store and dispose of these.
A. Low-molecular-weight heparin does not cross the placenta and therQefore 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. If you have any of the risk factors, you might need heparin during pregnancy.
You should thus see your obstetrician as early as possible so that heparin can be started at the right time.
The length of time you will be advised to stay on heparin depends on your risk factors and whether your situation changes.
It may be that treatment is recommended for only a few days to cover long-distance travel, or treatment may be recommended for the week immediately after delivery.
Sometimes, treatment may be recommended for the whole of your pregnancy and for up to 6 weeks after the birth.
A. If you think you are going into labour, do not have any more injections. Phone your obstetrician and tell her that you are on heparin treatment. He/She will advise you what to do.
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 12 hours (24 hours if you are on a high dose) after your last injection. You will have the option of alternative pain relief.
If the plan is to induce labour, you should stop your injections 12 hours (24 hours if you are on a high dose) before the planned date.
A. If your baby needs to be born by emergency caesarean section within 12 hours (24 hours if you are on a high dose) of your last heparin injection you will not be able to have an epidural or spinal injection and instead will need a general anaesthetic for your operation.
If you are having a planned caesarean section, your last heparin injection should be 12 hours (24 hours if you are on a high dose) before the planned caesarean delivery. Heparin will usually be restarted within 4 hours of the operation.
A. It is important to be as mobile as possible after you have had your baby and to avoid becoming dehydrated.
A risk assessment will be carried out after the birth of your baby.
Even if you weren’t having injections in pregnancy, you may need to start heparin injections for the first time after birth. This will depend on what risk factors you have for a DVT. You may be advised to have heparin for 7–10 days after birth or sometimes for 6 weeks after birth.
If you were on heparin before the baby’s birth, you are likely to be advised to continue this for 6 weeks afterwards.
A. At your postnatal appointment, your obstetrician would:
A. Yes – both heparin and warfarin are safe to take when breastfeeding.