Pregnancy is a risk factor for developing venous thromboembolism (VTE). By assessing a womans individual risk during pregnancy then appropriate prophylactic measures can be initiated. A risk assessment should be completed at booking and on any subsequent hospital admission.

A woman with a previous VTE history is automatically considered high risk and requires low molecular weight heparin throughout the antenatal period and also input from experts.

A woman at intermediate risk of developing VTE due to hospitalisation, surgery, co-morbidities or thrombophilia should be considered for antenatal prophylactic low molecular weight heparin.

The assessment at booking should include risk factors that increase the womans likelihood of developing VTE. These risk factors include:

• Age > 35
• Body mass index > 30
• Parity > 3
• Smoker
• Gross varicose veins
• Current pre-eclampsia
• Immobility
• Family history of unprovoked VTE
• Low risk thrombophilia
• Multiple pregnancy
• IVF pregnancy

Four or more risk factors warrants immediate treatment with low molecular weight heparin continued until six weeks postnatal. If a woman has three risk factors low molecular weight heparin should be initiated from 28 weeks and continued until six weeks postnatal.

If diagnosis of DVT is made shortly before delivery, continue anticoagulation treatment for at least 3 month, as in other patients with provoked DVTs.

Low molecular weight heparin is the treatment of choice for VTE prophylaxis in pregnancy. Direct Oral Anticoagulants (DOACs) and warfarin should be avoided in pregnancy.

LMWH does not cross the placenta, other drugs do.