11/14/24, 10\:39 AM Venous Thromboembolism in Pregnancy and the Puerperium

Venous Thromboembolism in Pregnancy and the Puerperium

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VTE in pregnancy\: includes deep vein thrombosis (DVT) and pulmonary embolism (PE); major direct cause of maternal
death.
Risk\: increases 4-6 times during pregnancy, absolute incidence ~1 in 1000 cases.
Aetiology\: pregnancy increases blood coagulability via increased coagulation factors (VIII, IX, X),

Risk factors\:
Antenatal\: previous non-provoked VTE, mechanical heart valve, high-risk thrombophilia, immobility, dehydration, medical
comorbidities, surgery, BMI >30, age >35, parity >3, smoking, varicose veins, pre-eclampsia, family history of VTE, multiple
pregnancy, IVF.
Postnatal\: previous VTE, antenatal LMWH, high-risk thrombophilia, caesarean section, BMI >40, prolonged admission,
surgery post-delivery, medical comorbidities, elective caesarean, family history of VTE, varicose veins, infection, immobility,
pre-eclampsia, multiple pregnancy, pre-term delivery, stillbirth, prolonged labour, post-partum haemorrhage.
Clinical features\:
DVT\: unilateral limb pain and swelling, erythema.
PE\: dyspnoea, tachypnoea, pleuritic chest pain, haemoptysis, symptoms of DVT.
Examination
DVT\: unilateral limb oedema, erythema, warmth, venous distension, tenderness.
PE\: tachycardia, tachypnoea, hypoxia, fever, pleural rub, gallop rhythm, haemodynamic instability in massive PE.
Investigations\:
Bedside\: basic observations, pulse oximetry, ECG.
Laboratory\: FBC (raised WCC).
Imaging\: compression duplex ultrasound (DVT), V/Q scan or CTPA (PE).
Management\:
Prophylaxis\: early risk assessment, LMWH, avoid warfarin and DOACs.
Treatment\: LMWH initiated on clinical suspicion, avoid LMWH 24 hours before delivery, restart LMWH 4 hours after spinal
anaesthetic/epidural removal, continue treatment postnatally for at least 6 weeks or 3 months in total.
Complications\: sudden cardiac arrest (massive PE), acute limb ischaemia, post-thrombotic syndrome, recurrence, chronic
thromboembolic pulmonary hypertension (CTEPH).
Future family planning\: any VTE during pregnancy or puerperium indicates high risk in future pregnancies, requiring
antenatal treatment.
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A comprehensive topic overview

Introduction

Pregnant people are at increased risk of venous thromboembolism (VTE), and venous thromboembolism is an important
direct cause of maternal death. When discussing VTE, this article will consider deep vein thrombosis (DVT) and
pulmonary embolism (PE).
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Compared to people of the same age who are not pregnant, the risk of VTE increases between four and six times during
pregnancy. However, the absolute incidence remains low, at about one in a thousand cases.

Aetiology

During pregnancy, the blood becomes more coagulable. This is due to\:
Increased coagulation factors VIII, IX and X
Increased
Decreased
Reduced anti-thrombin levels
Reduced protein S levels
Increased venous stasis
Vascular damage
These changes can be considered protective against excessive blood loss at delivery. Accordingly, the risk of venous
thromboembolism increases throughout pregnancy, peaks at the baby's delivery, and slowly decreases back to baseline by
six weeks postpartum (Figure 1).
Figure 1. The rate of VTE in and around pregnancy
The absolute risk of VTE is low during early pregnancy - however, this is when most fatal VTE events occur. As such, some
form of early risk assessment is required to determine which women should be o
risk of VTE.
When managing people of child-bearing age with serious conditions such as mechanical heart valves or high-risk
thrombophilias, conversations about how these conditions and pregnancy interact should be had as early as possible.
Use local prescribing guidelines for speci
groups. These algorithms are not yet standardised and can be frustratingly vague, so more research is needed.

Risk factors

Antenatal VTE risk factors

Table 1. Risk factors for VTE occurring antenatally.
High risk Medium risk Low risk
Any previous non-provoked VTE
Mechanical heart valve Immobility, e.g. due to prolonged
hospital admission
Dehydration, e.g. due to hyperemesis High-risk thrombophilia, e.g.
antiphospholipid syndrome
BMI > 30kg/m
2
Age > 35
Parity > 3
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Medical co-morbidities, e.g. cancer,
IBD, SLE
Smoking
Surgery Gross varicose veins
Pre-eclampsia
History of unprovoked VTE in
degree relative
Multiple pregnancy
In-vitro fertilisation or assisted
reproduction

Postnatal VTE risk factors

Table 2. Risk factors for VTE occurring postnatally.
High risk Medium risk Low risk
Any previous VTE
Caesarean section
during labour (i.e. not an
elective case)
BMI > 30kg/m
2
2
Antenatal LMWH BMI > 40kg/m Age > 35
High-risk thrombophilia,
e.g. antiphospholipid
syndrome
Admission/readmission
for three or more days
after delivery
Parity > 3
Surgical procedure post-
delivery (apart from repair
of the perineum)
Smoking
Medical co-morbidities,
e.g. cancer, sickle cell
anaemia, SLE
Elective caesarean
section
Family history of VTE
Gross varicose veins
Current systemic
infection
Immobility, e.g.
paraplegia, journey > 4
hours
Pre-eclampsia
Multiple pregnancy
Pre-term delivery (\< 37
weeks)
Stillbirth in this
pregnancy
Prolonged labour > 24
hours
Post-partum
haemorrhage > 1L or
requiring blood
transfusion
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Clinical features

Signs and symptoms of DVT/PE in pregnancy are similar to those in non-pregnant patients.

History

Typical symptoms of a DVT include\:
Unilateral limb pain\: often described as cramping and may worsen over several days
Unilateral limb swelling
Erythema
Typical symptoms of a PE include\:
Dyspnoea
Tachypnoea
Pleuritic chest pain
Haemoptysis
Concurrent symptoms of DVT

Clinical examination

Typical clinical signs of DVT on examination may include\:
Unilateral limb oedema\: often pitting oedema
Erythema
Painful limb is warm to touch
Peripheral venous distension
Tenderness along the line of deep veins
Painful movement of the muscles distal to the thrombus
Typical clinical signs of a PE on examination may include\:
Tachycardia
Tachypnoea
Hypoxia
Low-grade fever
Pleural rub
Gallop rhythm\: a wide split-second heart sound and tricuspid regurgitant murmur
If a patient develops a massive PE, they may present with haemodynamic instability, collapse and an elevated jugular
venous pressure (JVP); this is a medical emergency.

Di

For more information on important diDVTs and PEs.

Investigations

VTE can be challenging to diagnose during pregnancy because symptoms such as shortness of breath and swollen legs
are common; as such, objective investigations are necessary for diagnosis.
Clinical prediction rules developed for the non-pregnant population are not validated for use in pregnant people and
should not be used. (e.g. Well's Score)

Bedside investigations

Relevant bedside investigations include\:
Basic observations\: should be carried out on all patients with suspected VTE. Pulse oximetry during exertion can be
useful in exacerbating the ventilation-perfusion mismatch and monitoring the resulting hypoxaemia.
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ECG\: should be considered in suspected PE to help rule out di

Laboratory investigations

Relevant laboratory investigations include\:
Full blood count (FBC)\: may show a raised white cell count due to acute in
diagnoses
D-dimer
D-dimer is not indicated in pregnancy as it will give a false positive result.

Imaging

If DVT is suspected, patients will often be initiated on anticoagulation until imaging can be carried out; compression
duplex ultrasound is the primary diagnostic test.
If the ultrasound is positive, then anticoagulant treatment should be continued
If the ultrasound is negative but clinical suspicion remains high, maintain the treatment and repeat the ultrasound on
days 3 and 7
If the ultrasound is negative and clinical suspicion is low, stop treatment
If PE is suspected but DVT is also suspected, investigate for DVT with compression duplex ultrasound. If it is positive, no
other investigations are necessary, as the treatment for DVT and PE is the same.
If PE is suspected but without signs and symptoms of a DVT, a ventilation/perfusion (V/Q) lung scan or a computerised
tomography pulmonary angiogram (CTPA) should be performed.
These investigations involve radiation, and so there are concerns over the increased risk of developing cancer (foetal for
V/Q; breast for CTPA). Explain to patients that these potential risks are extremely small. No large experimental studies have
veri

Management

VTE prophylaxis in pregnancy

Patients should undergo a risk assessment early in pregnancy (and a re-assessment if their health changes signi
and following delivery to determine whether prophylaxis is appropriate.
Guidelines for risk assessment may vary between hospitals, but the Royal College of Obstetricians and Gynaecologists has
produced an example risk assessment that can be used (Figure 2).
Figure 2. RCOG obstetric thromboprophylaxis risk assessment
VTE can be prevented with daily dosing of Low Molecular Weight Heparin (LMWH). Local guidelines in your hospital set
the particular version of LMWH and the weight-based dosage.
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Other anticoagulants
Warfarin can cross the placenta and a
oral anticoagulants (DOACs) are usually avoided due to the lack of reversal agents in case of bleeding.
In the acute setting, if the half-life of LMWH is considered too long, infusions of unfractionated heparin are an option.

Treating VTE in pregnancy

VTE is rare, but the risk of death plus the relative ease and safety of treatment means that there is a low threshold for
treatment once there is a clinical suspicion. Start LMWH treatment dose and organise de
as soon as possible.
VTE is often overlooked when pregnant people present outside of a traditional antenatal context, such as miscarriage or
hyperemesis. It can also be neglected when pregnancy is detected incidentally. Consider VTE risk whenever managing a
pregnant patient in the acute setting.
Treatment usually involves a once-daily, weight-based dosing of LMWH. Follow local guidelines. In non-standard cases, a
haematologist may advise a twice-daily regime.
Due to the risk of dangerous haemorrhage, LMWH therapy should be stopped 24 hours before delivery. Practically, the
patient should be advised that once they are in established labour, they should not self-administer any further medication.
LMWH is usually not restarted until 4 hours after the use of spinal anaesthetic or removal of the epidural catheter to
reduce the risk of developing spinal haematomas.

Treatment in the puerperium

Any antenatal treatment should be continued until at least six weeks postnatally or three months in total, whichever is
longer. As the baby is delivered, the risk to the foetus is eliminated, and the patient can decide to switch to oral medications
such as warfarin, even if they are breastfeeding. There is less safety data regarding breastfeeding and direct oral
anticoagulants, so seek expert advice and have careful discussions with the parents.
Postnatal presentation of VTE is common. VTE diagnosed within six weeks of delivery is considered provoked by the
pregnancy and so would be managed with a three-month course of anticoagulation.

Complications

Complications of DVT and PEs are similar in pregnancy to the rest of the population and include\:
Sudden cardiac arrest\: in the case of massive PE
Acute limb ischaemia
Post-thrombotic syndrome\: residual pain, swelling and erythema. This can a
Increased risk of recurrence
Chronic thromboembolic pulmonary hypertension (CTEPH)
Future family planning
Any VTE diagnosed during pregnancy or the puerperium would count as a high-risk factor in future pregnancies
and so call for antenatal treatment. It is pertinent to discuss this with the patient as it might a
expand their family.

References

Crosby, David A, et al. Antenatal venous thromboembolism. The Obstetrician & Gynaecologist 23.3 (2021)\: 206-212
Reducing the Risk of Venous Thromboembolism during pregnancy and the Puerperium. Green-top Guideline No 37a. Royal
College of Obstetricians and Gynaecologists (Great Britain). British Journal of Obstetrics and Gynaecology. April 2015.
https\://app.geekymedics.com/notebook/2823/ 6/711/14/24, 10\:39 AM Venous Thromboembolism in Pregnancy and the Puerperium
Bĕlohlávek J, Dytrych V, Linhart A. Pulmonary embolism, part I\: Epidemiology, risk factors and risk strati
pathophysiology, clinical presentation, diagnosis and nonthrombotic pulmonary embolism. Exp Clin Cardiol. 2013
Spring;18(2)\:129-38. PMID\: 23940438; PMCID\: PMC3718593.

Image references

Figure 1. Abdul Sultan, A., Tata, L. J., Grainge, M. J., & West, J. (2013). The incidence of
around pregnancy using linked primary and secondary care data\: a population based cohort study from England and
comparative meta-analysis. P l o S o n e , 8 (7), e70310.
Figure 2. Reproduced from\: Royal College of Obstetricians and Gynaecologists. Reducing the Risk of Venous
Thromboembolism during Pregnancy and the Puerperium). Green-top Guideline No. 37a. London\: RCOG, April 2015, with
the permission of the College

Reviewer

Miss Avni Batish MBBS, MRCOG

Related notes

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Antenatal Screening for Down’s Syndrome
Antepartum Haemorrhage (APH)
Breech Presentation
Caesarean Section

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Contents

Introduction
Aetiology
Risk factors
Clinical features
Di
Investigations
Management
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