Pregnancy associated venous thrombosis (DVT)

June 4, 2012 in Life

DVT in pregnancy

© Dmitry Kuznetsov |

This guest post, about pregnancy associated DVT, is by Eddie Chaloner from Radiance Health.

Deep vein thrombosis (or DVT) is a condition where a blood clot forms in the deep veins of the legs. As a consequence of the clot, the leg can swell up and become very painful although in rare cases the clot can be ‘clinically silent’ – i.e. cause no pain at all.

DVT can complicate approximately 1 in 1,000 pregnancies, which doesn’t sound like a large number but as there are about 700,000 babies born each year in the UK that results in 700 DVTs as a consequence of pregnancy. DVTs can occur in ladies who are not pregnant but pregnancy does increase the risk of DVT very substantially, and many of the patients we talk to at Radiance Health for DVT have developed the condition during pregnancy.

The reason people get concerned about DVT is that untreated the clot can spread and sometimes detach from the vein wall. If this happens to a big piece of clot, it can travel in the bloodstream into the lung circulation and cause a pulmonary embolus, which is when the clot gets jammed in one of the arteries supplying the lungs. If the clot gets stuck in one of the main pulmonary (lung) arteries, it can be a life threatening condition. Fortunately, prompt diagnosis and treatment of a DVT will greatly reduce the chances of this happening.

DVT is more likely to occur in the later stages of pregnancy when the swollen uterus presses on the veins in the pelvis, but it can occur at any stage of pregnancy or in the 6 weeks following delivery. Patients who have had a caesarean section are more likely to get a post pregnancy DVT than patients who delivered normally.

Some women are at higher risk of developing a DVT than others. Women over 35, women with a past history of having had a DVT (or a family history of DVT) or women with one of the known blood disorders which predispose people to getting DVTs are all more likely to have DVTs in pregnancy than people without these factors.

Other risk factors include being overweight, smoking, multiple pregnancy (i.e. twins etc) or pre eclampsia (a condition that can develop during pregnancy that causes the blood pressure to rise to dangerously high levels).

Wearing graduated compression stockings can reduce the risk of DVT  but does not eliminate the risk entirely. In particularly high risk cases the pregnant woman might receive a precautionary low daily dose of an anti-coagulant drug called heparin (see more below).

A DVT is diagnosed by an ultrasound scan – this is done quite easily and painlessly but it does need to be performed by a radiologist or technician expert and practiced in the use of vascular ultrasound. In the right hands this will reliably diagnose or exclude a DVT in a patient with a swollen leg.

The treatment for DVT is currently anti-coagulation – this is where the blood is ‘thinned’ by use of drugs. Most commonly in pregnancy a drug called heparin is used which is injected under the skin once or twice a day- this is very similar to the way in which diabetics receive their insulin. Usually most patients can be taught to administer the heparin themselves at home rather than having to stay in hospital. Heparin does not cross the placenta, so it cannot harm the baby.

There are other anti-coagulant drugs, such as warfarin, which are often used in DVT. These can be taken orally as a tablet, but are not used in pregnancy as they are quite long acting drugs, whereas heparin is short acting. This is important because as labour approaches the heparin injections are stopped in cases the woman needs to have an epidural or a caesarean section – both of which can be dangerous if the blood is not clotting properly. The heparin is stopped for a few days around the time of birth and then restarted afterwards. After birth the heparin injections can be changed to warfarin tablets and the duration of treatment will depend on the type and severity of the DVT. Warfarin can be taken during breast-feeding but does need close monitoring with regular blood tests. There are newer anticoagulant drugs being evaluated which may be preferable to warfarin in the future.