When you are pregnant, you are at increased risk of blood clots forming in your veins.
Blood clots can cause serious conditions such as:
- deep vein thrombosis (DVT) - where a blood clot forms in a deep vein in your thigh, calf or pelvis
- pulmonary embolism (PE) - where part of a blood clot blocks a blood vessel in your lungs
These conditions are not common in pregnancy but need urgent medical help.
Urgent advice: Call your midwife, GP or maternity unit urgently if you have 1 or more of the symptoms of DVT:
- pain, swelling or tenderness in 1 leg - usually in your calf area
- warm or red skin over the affected area
- a heavy ache in the affected area
- pain in your calf that gets worse when you bend your foot up towards your knee
They usually only happen in 1 leg.
Emergency action required: Call 112 or 999 immediately if you:
- have chest pain or pain in your upper back
- have sudden difficulty breathing
- have pain when you breathe in
- are coughing up blood
These can be signs of a pulmonary embolism (PE).
You can have a PE without symptoms of a DVT.
Swollen ankles and legs are common in pregnancy and do not mean you have a DVT. But if you’re worried, phone your GP, obstetrician or midwife.
Causes of DVT or PE in pregnancy
Pregnancy and giving birth increase your risk of having a deep vein thrombosis (DVT).
This is because of:
- changes to your hormones
- changes to your circulation
- pressure from your growing baby on the veins in the lower part of your tummy and pelvis
The risk continues for 6 weeks after you give birth.
Clots can separate from your veins and travel to your lungs. Having a clot in your leg or pelvis increases the risk of a pulmonary embolism (PE).
People at higher risk of DVT
Some things can increase your risk of developing DVT.
Talk to your GP if you are pregnant or trying for a baby and you:
- had a blood clot before - or a close family member had a blood clot (mother, father or sibling)
- have a serious illness or injury
- are over age 35
- are overweight - especially if your BMI is over 30
- smoke
- inject drugs or medicines not prescribed by your doctor
- have a medical condition that makes blood clots more likely, called a thrombophilia
- have severe varicose veins
- have poor mobility, for example you are a wheelchair user
- have certain medical conditions - for example, lung disease, inflammatory bowel disease or autoimmune diseases such as lupus
Your GP or obstetrician may suggest treatment during pregnancy to prevent a blood clot.
During and after pregnancy, you may be at higher risk of DVT if you:
- travel for over 4 hours and you cannot move around, such as a taking a long-haul flight
- are expecting twins or more
- had fertility treatment
- become dehydrated or have severe sickness in pregnancy (hyperemesis gravidarum)
- are staying in hospital and cannot move around much
- have pre-eclampsia
- have a caesarean birth
- lose a lot of blood after the birth
What happens at your appointment
If you have symptoms of a deep vein thrombosis (DVT), your GP or obstetrician will examine your leg. They will measure your calves to compare both sides.
They may refer you for an ultrasound scan of your leg to check for a clot.
If a DVT seems likely, they may start you on treatment while they wait for your scan. If the scan shows that you do not have a DVT, they will tell you to stop the treatment.
Treatment for a DVT
Treatment for DVT in pregnancy is usually heparin injections. Heparin is a blood-thinning medicine. It stops the blood clot getting bigger so your body can dissolve it. Heparin also reduces the risk of a pulmonary embolism.
Heparin is safe to use during pregnancy and does not affect your baby.
Your GP or obstetrician will show you how to give yourself the injections. If you prefer not to do injections yourself, they can show your partner or a support person how to give injections.
You will usually continue heparin treatment until your baby is 6 weeks old.
Other things you can do to help
To manage your DVT, your doctor or midwife may recommend that you:
- wear compression stockings - you can get a prescription for these
- stay as active as possible
Managing pulmonary embolism (PE) in pregnancy
Your obstetrician or hospital doctor will examine you and may order some blood tests.
If they think you have a PE, they may order other tests, such as a:
- chest x-ray - to check for other causes of shortness of breath, such as a chest infection
- CT scan of your lungs
- ventilation and perfusion (VQ) scan - to check your lungs for PE, there are 2 parts to the scan
Safety of x-rays and scans in pregnancy
You may be exposed to a small amount of radiation when you have an x-ray, CT scan or VQ scan.
The amount of radiation in a chest x-ray is so small that it will not harm you or your baby.
CT scans and VQ scans have slightly more radiation. They have never been shown to cause harm to an unborn baby.
If your health is in danger from a PE, the benefits of having these tests far outweigh any small risks. Your doctor will discuss the benefits and risks of the tests with you.
They will only do a CT scan or a VQ scan if it's really needed.
Treatment for a PE
Treatment for a PE is usually heparin injections. The length of the treatment depends on when the PE developed during the pregnancy.
Reducing your risk of DVT
To reduce your risk of developing a DVT in pregnancy:
Do
-
get help to stop smoking if you smoke
-
maintain a healthy weight before you get pregnant
-
drink enough fluids to avoid dehydration
-
wear compression stockings if your obstetrician, hospital doctor or midwife prescribes them
