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  • HSIB - The assessment of venous thromboembolism risks associated with pregnancy and the postnatal period final report (8 December 2022)

    Article information
    • UK
    • Investigations
    • Pre-existing
    • Original author
    • No
    • Healthcare Safety Investigation Branch
    • 08/12/22
    • Everyone


    This investigation by the Healthcare Safety Investigation Branch (HSIB) explores the issues associated with the assessment of risk factors for venous thrombosis in pregnancy and the first six weeks after birth. Venous thrombosis occurs when a blood clot forms and causes a blockage in a person’s vein. This can lead to venous thromboembolism (VTE), when part of the clot breaks off and travels through the bloodstream, blocking a blood vessel elsewhere in the body.

    Pregnant women and pregnant people are at greater risk of developing a venous thrombosis than those who are of the same age and not pregnant. Because of the increased risk, healthcare staff assess a pregnant woman’s risk factors for VTE at key stages before and after the birth, so that they can be given preventative treatment if necessary. While rare, in the UK venous thrombosis and VTE is the leading direct cause of death of pregnant women during pregnancy or up to six weeks after the end of pregnancy.

    Reference event

    The reference event for this investigation was the case of Alice, who was 26 years old and was pregnant with her second child. A VTE risk assessment was completed for Alice at her first antenatal appointment, when she was admitted to hospital for the birth of her child, and 24 hours after admission. Her score was zero each time, meaning no risk factors were identified for VTE. During her pregnancy Alice reported experiencing some pain in her calf; she was examined by a doctor who referred her for a scan. This ruled out a deep vein thrombosis (DVT).

    After giving birth by caesarean section, Alice's risk assessment was repeated, and as it indicated that medication was required, a preventative dose of low-molecular-weight heparin was prescribed and Alice was discharged. Eleven days after the birth of her baby, Alice was taken by ambulance to the emergency department with chest pain, shortness of breath and leg cramps. She was diagnosed with a pulmonary embolism (PE) and was started on a treatment dose of blood-thinning injections. Following investigation, it was found that Alice may not have received an appropriate preventative dose of low-molecular-weight heparin to help prevent the VTE.



    • For healthcare staff, carrying out a robust assessment of risk factors for VTE is challenging, particularly in the complex and busy environment of antenatal clinics, the labour ward and on postnatal wards.
    • Multiple competing demands, exacerbated by distractions and interruptions, mean healthcare professionals are constantly having to balance risk and safety for the pregnant women/pregnant people they care for and are trading off the thoroughness of assessments to improve efficiency.
    • Midwives are asked to complete a number of risk assessments and screening tools to assess pregnant women’s/pregnant people’s risk at their first antenatal appointment (known as the booking appointment). However, the time needed to carry out these risks assessments may not be reflected in the time allocated for appointments.
    • Risk assessments and screening tools are not all designed and presented in a consistent and logical way that would aid staff in completing the task.
    • Assessment of VTE risk factors should take place routinely due to body changes in pregnancy and increased risk of VTE.
    • Although assessing VTE risk is important, it is a relatively rare condition and there are a number of other competing risks that may take priority.
    • Staff do not always involve pregnant women and pregnant people in, or discuss with them, the assessment of their risk factors for VTE. This means pregnant women and pregnant people may not be aware of the signs and symptoms of a possible VTE.
    • The importance of knowing the signs and symptoms of VTE may not be fully understood or prioritised by pregnant women and pregnant people who may have other competing concerns and questions about their antenatal and postnatal care.
    • National guidance recommends that assessment of VTE risk factors should be repeated when a pregnant woman/pregnant person presents with an ‘intercurrent problem’ (a new health issue which may or may not be related to the pregnancy). However, not all healthcare professionals understand the meaning of ‘intercurrent problem’ and therefore opportunities to reassess risk factors are missed.
    • There is a mix of paper-based and electronic record keeping in antenatal and postnatal care. Electronic records systems may lack interoperability and suffer from poor connectivity which limits the ability of staff to access all the data, information, and knowledge they need at the time of assessment.
    • Recommendations by MBRRACE-UK (Mothers and Babies: Reducing Risk through Audits and Confidential Enquiries across the UK) for the development of a tool to make the current assessment of VTE risk factors simpler and more reproducible, have not been acted on.

    Safety observations

    • It may be beneficial for organisations to consider guidance, such as the ‘principles for effectiveness and usability’ provided by the Chartered Institute of Ergonomics and Human Factors, when developing risk assessment tools. The aim being to ensure assessments are simple to use and therefore staff being more likely to do them thoroughly and avoid tick-box fatigue.
    • It may be beneficial for organisations that make recommendations to improve the safety and care of pregnant women and pregnant people during their pregnancy and up to 6 weeks after birth, to have a process for reporting on responses to their recommendations. This would support transparency, making it easy to see what has been achieved and what remains outstanding. The aim being to enable tracking of the implementation of actions designed to improve safety and outcomes to ensure they happen.
    • It may be beneficial if future research or funding is directed towards identifying the evidence base for the prescribing of low-molecular-weight heparin for venous thromboembolism risk in pregnancy and the first 6 weeks after birth. This will support the production of evidence-based clinical guidelines for the care and treatment of pregnant women and pregnant people at risk of VTE to ensure it is safe and effective.
    HSIB - The assessment of venous thromboembolism risks associated with pregnancy and the postnatal period final report (8 December 2022) https://www.hsib.org.uk/investigations-and-reports/the-assessment-of-venous-thromboembolism-risks-associated-with-pregnancy-and-postnatal/
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