Deep vein thrombosis: reducing the risk during pregnancy and after birth

Thrombosis is a blood clot that has formed in a blood vessel in the body. Veins are blood vessels that return blood from areas of the body back to the heart. A Deep Vein Thrombosis (or a DVT) is a blood clot that forms in one of the deep veins in the body, usually in the leg (calf or thigh) or pelvis.

A DVT can cause blockage to the flow of blood in that vein which can cause pain, swelling and discomfort in the leg.

A DVT can be serious because part of the blood clot (embolus) can break off and travel up the vein, through the heart and into the lungs. The clot can then lodge in the blood vessels in the lungs and block the circulation of blood. This is called a Pulmonary Embolus (a PE) and can be life-threatening.

The symptoms of PE can include:

• Breathing difficulties which can occur suddenly.
• Chest pains or a tight feeling in the chest.
• Coughing up blood.
• Feeling very unwell or collapsing.

Being pregnant increases your risk of getting a DVT. This increased risk exists throughout your whole pregnancy, including the first three months, and lasts up to six weeks after the birth of your baby. The highest risk for you having a DVT is just after birth.

Fortunately DVT is still an uncommon event to happen in pregnancy and occurs in only one or two women in every 1,000.

Aside from pregnancy itself, there are certain situations and conditions that increase your risk of getting a DVT or PE. These are called risk factors. Your risk of getting a DVT or PE in pregnancy is higher with any of the following risk factors:

Before Pregnancy:

• If you are over 35 years of age.
• If you have had three or more babies.
• If you or members of your immediate family (parents and siblings) have had a previous DVT or PE.
• If you have a medical condition that makes your blood clot more easily (thrombophilia).
• If you have been diagnosed with other medical conditions such as heart or lung disease or arthritis which increase your risk of having blood clots (your doctor or midwife will know which conditions these may be).
• If you have severe varicose veins that are painful or above the knee with redness and/or swelling.
• If you are a wheelchair user.

Lifestyle:

• If you smoke.
• If you are overweight with a body mass index (BMI) of 30 and over.
• If you use intravenous drugs.
• If you have a sedentary lifestyle.

During Pregnancy:

• If you are admitted to hospital.
• If you are pregnant with more than one baby.
• If you become dehydrated in pregnancy, for example, with vomiting in early pregnancy.
• If you become unwell with conditions such as severe infection or kidney stones.
• If you become less mobile for long periods of time for example after an operation or travelling distances longer than 4 hours by air, car or train.
• If you become unwell from fertility treatment (Ovarian Hyperstimulation Syndrome).
• If you develop a condition called pre-eclampsia.

After your baby has been born:

• If your labour was very long (more than 24 hours).
• If you have had a caesarean section.
• If you lost a lot of blood during your delivery or required a blood transfusion.

Your risk of getting DVT can change throughout your pregnancy so it is important that your risk is assessed throughout at various points:

Before Pregnancy.

If you are planning a pregnancy and have any of the risk factors above you should have a discussion with your GP. You may need to be referred to see an obstetrician to discuss your risk of DVT prior to you getting pregnant or early on in your pregnancy.

If you have had a previous DVT and are already taking medicines to thin your blood, such as warfarin, you should ask your GP to be referred to an obstetrician who will advise on your blood thinning treatment through your pregnancy. You may also need to change your blood thinning medication from tablets to injections (heparin).

During and After Pregnancy.

Your risk of getting a DVT will be assessed by your midwife at your booking appointment and again at your 28-week appointment.

If you are admitted to hospital or you develop any of the risk factors above, a risk assessment will be repeated by the doctor or midwife looking after you.

After your baby is born your risk will be assessed again.

To reduce your risk of getting DVT:

• Stay well hydrated by drinking regular amounts of fluid.
• Stay active throughout your pregnancy.
• Wear special stockings (Graduated Compression Stockings).
• Stop smoking.

DVT prophylaxis is medication to thin the blood (anticoagulant) to help prevent blood clots developing. This is normally with a medication called heparin. The name of heparin used at BSUH is called Enoxaparin.

Heparin is also used as treatment for DVT but much higher doses are used in this situation.