Advice on preventing and treating venous thromboembolism (VTE) during pregnancy, birth and following delivery is outlined in two new revised guidelines published today (13 April) by the Royal College of Obstetricians and Gynaecologists (RCOG) and launched at the RCOG World Congress in Brisbane, Australia.
VTE refers to the formation of a clot within veins. This can occur anywhere in the venous system, but the predominant sites are in the vessels of the leg (giving rise to deep vein thrombosis (DVT)) and in the lungs (resulting in a Pulmonary embolism (PE)).
The Green-top Guidelines provide information, based on clinical evidence, to assist clinicians with both the prevention and treatment of VTE in pregnant women, a condition which remains the leading direct cause of maternal death in the UK.
VTE is uncommon in pregnancy or in the first 6 weeks postnatally and the absolute risk is around 1 in 1,000 pregnancies. It can occur at any stage in pregnancy, but the time of the highest risk is the first 6 weeks following birth, when the risk increases 20-fold.
Risk factors include previous VTE or thrombophilia (a tendency to form blood clots), obesity, increased maternal age, immobility and long-distance travel, admission to hospital during pregnancy and other comorbidities such as heart disease, inflammatory bowel disease and pre-eclampsia.
Additional risk factors occurring during the first trimester of pregnancy include hyperemesis gravidarum, ovarian hyperstimulation and IVF pregnancy. Caesarean section is also a risk factor.
Venous thromboembolism (VTE) refers to the formation of a thrombus within veins. This can occur anywhere in the venous system but the clinically predominant sites are in the vessels of the leg (giving rise to deep vein thrombosis (DVT)) and in the lungs (resulting in a pulmonary embolus (PE)).
The pathophysiology of VTE in pregnancy appears to relate to the increased venous stasis noted during this period but other factors such as alterations in the balance of proteins of the coagulation and fibrinolytic systems have also been implicated.
The guidelines emphasise that all women should undergo a thorough assessment for VTE in early pregnancy or pre-pregnancy and again intrapartum or immediately postpartum.
Any woman with risk factors should be considered for prophylactic low-molecular-weight-heparin (LMWH), an injection administered to thin the blood. The duration of treatment depends on the number of risk factors a woman has. It may be offered both antenatally and after the baby is born.
In addition, women with previous VTE must be offered pre-pregnancy counselling. A prospective management plan for VTE should also be made, including appropriate treatment to be offered as early as possible and a careful history documented.
- VTE affects about 1 in 100,000 women of childbearing age.
- It is up to 10 times more common in pregnant than in non-pregnant women of a similar age.
- It occurs in about 1/1,000 pregnancies in women under the age of 35.
- It occurs in 2.4/1,000 pregnancies in women over the age of 35.
- Inherited thrombophilia is present in 30-50% of women with pregnancy-associated VTE.
- 10-20% of VTEs are PEs which are the main contributors to VTE mortality. They are the leading direct cause of maternal mortality in the UK, being responsible for a third of maternal deaths.
The guidance on treating VTE focuses on the acute management of the condition and highlights the signs and symptoms, including leg pain and swelling, lower abdominal pain, shortness of breath, chest pain, coughing blood and collapse.
Any woman presenting with signs and symptoms suggestive of VTE should be tested for the condition immediately and offered treatment with low-molecular-weight heparin (LMWH). All hospitals should have a protocol for the diagnosis of suspected VTE, with the involvement of a multi-disciplinary team of obstetricians, radiologists, physicians and haematologists.
Professor Catherine Nelson-Piercy, lead author of the guidance on preventing thromboembolism says: “Venous thromboembolism is rare in pregnancy and with prompt recognition can be treated effectively. This guidance provides clinicians with accurate scientific-based guidelines on the risk factors for VTE, as well as on how to prevent and treat the condition.
“It is vital that VTE is discussed with all women who are at risk and the reasons for individual treatment recommendations must also be explained.”
Dr Andrew Thomson, lead author of the guideline on treating thromboembolism and co-Chair of the RCOG Guidelines Committee says: “Previous editions of these guidelines have been credited with a reduction in the number of women dying from thromboembolism during their pregnancy or in the postnatal period in the UK. Nonetheless, thromboembolism remains an important cause of maternal morbidity and mortality in our country.
“These updated guidelines provide new evidence about risk factors for thrombosis in pregnancy and strategies that should be employed to reduce the chances of a thrombosis occurring. Furthermore, the guidelines provide updated information on the way women with a suspected thrombosis should be investigated and treated.”
RCOG/RANZCOG World Congress 2015