Risk assessment for thromboprophylaxis is ongoing throughout pregnancy and should take place during key phases in the woman’s maternity care journey. At a minimum this would include:

• At Booking
• At 28 weeks
• During any antenatal in-patient admission
• Post-birth in the labour ward setting
• Prior to postnatal discharge
• During any postnatal readmission

All women should be reweighed at 28 weeks’ gestation and postpartum to more accurately determine their VTE risk score and the appropriate prophylactic dose of LMWH (MBRRACE 2021).

The following table details the range of factors that increase the likelihood of VTE. 

Risk factors for VTE in pregnancy and the puerperium (RCOG GTG 37a, 2015):

The following table details the range of factors that increase the likelihood of VTE (RCOG GTG 37a). 

Each risk factor is allocated a score between 1 and 4. The use of antenatal and postnatal thromboprophylaxis will depend on the total risk score as follows:

• If total score ≥ 4 antenatally, consider thromboprophylaxis from the first trimester
• If total score 3 antenatally, consider thromboprophylaxis from 28 weeks
• If total score ≥ 2 postnatally, consider thromboprophylaxis for at least 10 days
• If admitted to hospital antenatally consider thromboprophylaxis
• If prolonged admission (≥ 3 days) or readmission to hospital within the puerperium consider thromboprophylaxis

The total risk score will be calculated automatically in the VTE Risk Assessments section of the electronic patient record (BadgerNet).

For patients with an identified bleeding risk, the balance of risks of bleeding and thrombosis should be discussed in consultation with a haematologist with expertise in thrombosis and bleeding in pregnancy.

Following comprehensive history-taking the Midwife/Doctor will complete and document their risk assessment findings within the woman’s BadgerNet maternity case records. 

Supporting tools include: 

• Thromboprophylaxis Risk Assessment and Management Quick Reference Guide [Appendix 1]
• VTE Risk Assessment User Guide 2022 [Appendix 2]
  • This user guide includes additional information to support the interpretation of risk factors
• Hospital Electronic Prescribing and Medicines Administration (HEPMA)

If the woman is identified as requiring thromboprophylaxis with LMWH it is essential that a care plan is made by a Healthcare Professional (HcP) and documented in the Actual Management Plan section within BadgerNet. The timing of thromboprophylaxis commencement will depend on the number of risk factors (see supporting appendices):

• Any HcP who is uncertain about the need for thromboprophylaxis or the ongoing management plan of patients should seek assistance from a colleague with an interest in medical disorders in pregnancy.
  
  
• Drug contraindications must be considered.
  
  
• Midwives can assess for and administer thromboprophylaxis. Prescribing thromboprophylaxis is an obstetric/medical remit.
• Some women, in the postnatal period, may be suitable for midwife administration and supply of postnatal thromboprophylaxis as per the Patient Group Direction (PGD) for enoxaparin. Midwives should refer to the PGD for more details.
• Women receiving antenatal thromboprophylaxis should be advised that if they experience any vaginal bleeding or once labour begins they should not inject any further LMWH until reviewed by an obstetrician and an ongoing plan of care documented.
  
  
• Breast-feeding is not contraindicated during post-natal thromboprophylaxis management with LMWH.

The LMWH preparation of choice in NHS GGC is enoxaparin. The appropriate dose is calculated from the woman’s most recent weight.

Other LMWH preparations that may be considered (for example if a woman develops an allergic skin reaction to enoxaparin) include dalteparin and tinzaparin. The doses of these LMWHs are also calculated from the woman’s most recent weight.

Infection with SARS-CoV-2 may also be associated with an overall increased risk of maternal VTE. This risk is likely to be multifactorial, including a hypercoagulable state associated with the infection, the reduced mobility resulting from self-isolation at home or hospital admission, and other associated obstetric or maternal morbidities (Coronavirus (COVID-19) Infection in Pregnancy – information for healthcare professionals. Version 15. 2022). 

The principles of care include:

• Women who are self-isolating at home should stay hydrated and mobile.
• Women should have a VTE risk assessment performed during their pregnancy in line with RCOG Green-top Guideline No. 37a. Infection with SARS-CoV-2 should be considered a transient risk factor and trigger reassessment.
• If healthcare professionals are concerned about the risk of VTE during a period of self- isolation, a clinical VTE risk assessment (in person or by virtual means) should be performed, and thromboprophylaxis considered and prescribed on an individual basis.
• Local procedures should be followed to ensure women are supplied with low molecular weight heparin (LMWH), particularly where they cannot attend hospital during periods of self-isolation.
• Thromboprophylaxis initiated for pregnant women who are self-isolating should be continued until they have recovered from the acute illness and are mobilising normally again.
• All pregnant women admitted with confirmed or suspected COVID-19 should be offered prophylactic LMWH, unless birth is expected within 12 hours or there is significant risk of haemorrhage.
• For women with severe complications of COVID-19, the appropriate drug and regimen of thromboprophylaxis should be discussed with a multidisciplinary team (MDT), including a senior obstetrician or clinician with expertise in managing VTE in pregnancy.
• All pregnant women who have been hospitalised and have had confirmed COVID-19 should be offered thromboprophylaxis for 10 days following hospital discharge. A longer duration of thromboprophylaxis should be considered for women with persistent morbidity.

If women are admitted with confirmed or suspected COVID-19 within 6 weeks postpartum, they should be offered thromboprophylaxis for the duration of their admission and for at least 10 days after discharge. Consideration should be given to extending this until 6 weeks postpartum for women with significant ongoing morbidity. 

Thromboprophylaxis during labour and delivery

• Women receiving prophylactic doses of LMWH during the antenatal period should be reviewed by a Senior Obstetrician before term (37+0 weeks) and a plan for labour/birth documented.
• It is important to discuss the implications of treatment with LMWH for regional anaesthesia and analgesia with the women before labour or caesarean section – the obstetrician (and/or obstetric anaesthetist) should inform all women taking LMWH about regional anaesthesia and labour. All women should be given access to the patient information leaflet – ‘Information for pain relief during labour or delivery for pregnant patients on blood thinning medications’ (available on Staffnet and on BadgerNet).

Regional anaesthesia or analgesia 

• This may be considered following discussion with a senior anaesthetist
• An individual management plan should be documented in the patient’s notes

To minimise or avoid the risk of epidural haematoma

• Regional techniques should not be used until at least 12 hours after the previous prophylactic dose of LMWH
• When a woman presents while on a therapeutic regimen of LWMH regional techniques should not be employed for at least 24 hours after the last dose of LMWH.
• LMWH should not be given for 4 hours after use of spinal anaesthesia or after the epidural catheter has been removed; the epidural catheter should not be removed within 12 hours of the most recent injection.

To be completed for every woman by the Midwife/Doctor:

• immediately following delivery prior to transfer to postnatal ward
• on postnatal readmission

The Postnatal VTE Risk Assessment form should be completed on BadgerNet. The result of the VTE Risk Assessment should also be included in the Postnatal Management Plan section within BadgerNet.

Prescription, if required, should be completed in the Hospital Electronic Prescribing and Medicines Administration (HEPMA) prior to transfer to the ward.

Early mobilisation and avoidance of dehydration is recommended for all postnatal women.

For women with a risk score of > 2 postnatally, it is recommended that thromboprophylaxis with LMWH is offered and administered for at least 10 days. LMWH dosage is graduated based on the woman’s most recent weight. 

For women considered to be at higher risk of postpartum VTE (for example women who required LMWH thromboprophylaxis antenatally), the recommended duration of thromboprophylaxis is 6 weeks. VTE risk assessment should be continued in the postnatal period and the decision to extend thromboprophylaxis beyond 10 days should be made by a senior clinician.

Women who require LMWH injection on discharge from the ward setting should be encouraged and supported to self-administer in the community setting.

Women will be shown the correct method by the ward midwife and have the opportunity to self-administer under supervision and this should be documented in the patient’s electronic record. 

The evidence supporting the use of graduated elastic compression stockings is varied. Pregnant women considered to be at an increased risk of VTE and have a contraindication to LMWH, should be advised to wear AES when immobilised/hospitalised during the antenatal period (RCOG 2015, SIGN 2010).

Accurate fitting and careful instruction in the correct application of the hosiery is essential to avoid discomfort and assist rather than prevent venous return.

For women who are risk of VTE postnatally and have a contraindication to LMWH, AES should be considered. Compliance factors should be evaluated and the option of below the knee AES explored. 

APPENDIX 1 Thromboprophylaxis Risk Assessment and Management Quick Reference Guide (pdf)

APPENDIX 2: VTE risk assessment– User guide 2022 (pdf)