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. 2024 Oct 29;25(1):20–28. doi: 10.1016/j.bjae.2024.09.004

Peripartum management of the patient taking anticoagulant medications

SC Reale 1,⁎, MK Farber 1
PMCID: PMC11897439  PMID: 40083962

Learning objectives.

By reading this article, you should be able to:

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    Identify reasons why patients may require anticoagulation during pregnancy.

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    Understand the classes and types of anticoagulant drugs used during pregnancy.

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    Describe the appropriate timing of neuraxial anaesthesia in relation to anticoagulant drugs.

Key points.

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    Venous thromboembolism is an important cause of maternal morbidity and mortality.

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    Parturients at increased risk for VTE may be prescribed prophylactic or treatment doses of anticoagulants.

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    Anticoagulants should be stopped and restarted at appropriate times to avoid neuraxial haematoma.

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    National guidelines include withholding prophylactic unfractionated heparin for at least 4 h, and low-molecular-weight heparin for at least 12 h, before neuraxial block.

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    Antenatal anaesthetic counselling is needed for patients taking anticoagulant drugs.

Venous thromboembolism (VTE) is an important cause of maternal morbidity and mortality, most recently accounting for 10–14% of maternal deaths in the USA and the UK.1,2 The risk of VTE increases approximately five-fold during pregnancy, and 20-fold in the postpartum period.3,4 The main factors associated with VTE during pregnancy are hypercoagulability, immunomodulation and venous stasis. The overall prevalence of VTE during pregnancy is two per 1000 deliveries, with 80% of thromboses being venous and 20% being arterial.3 Approximately 80% of VTEs are deep venous thromboses (DVTs) and 20% are pulmonary emboli (PE).3 In addition, women admitted to hospital for three or more days in the peripartum period for reasons other than delivery are at 12-fold increased risk of experiencing VTE.5 Patients with a personal history of prior VTE in pregnancy have up to 10% risk of recurrent VTE in a subsequent pregnancy if they do not receive thromboprophylaxis.6 This hypercoagulable state during pregnancy is secondary to a combination of physiologic and immunomodulatory factors (Fig. 1).7

Fig 1.

Fig 1

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Pathophysiology of venous thromboembolism in pregnancy.7 Reproduced with permission.

Although the absolute risk of VTE during pregnancy is relatively low, there is a need to risk stratify patients appropriately to determine who would benefit from prophylactic thromboprophylaxis. Indications for anticoagulation during pregnancy include a history of VTE, recognised risk for VTE (homozygous factor V Leiden, protein S and C deficiencies, prothrombin gene mutation, etc.), or recurrent pregnancy loss.8 A small number of women have an indication for long-term anticoagulation therapy predating pregnancy, including those with valvular heart disease and atrial fibrillation. Other clinical risk factors for VTE such as obesity, Caesarean delivery, advanced maternal age, pre-eclampsia and multiple gestation also increase the risk for VTE.9 Pregnant patients are increasingly being prescribed anticoagulant medications to prevent or treat the morbidity associated with VTE. Data from the UK's Mothers and Babies: Reducing Risk through Audits and Confidential Enquiries across the UK (MBRRACE-UK) report, dating from 1985 to 2021, have demonstrated similar rates of VTE over time despite increased rates of anticoagulant use.2 This may result from an increased risk of VTE-related comorbidities among obstetric patients that would otherwise have led to increased rates of VTE without thromboprophylaxis.

Challenges to the implementation of thromboprophylaxis remain; an analysis of three different societal recommendations for obstetric VTE prophylaxis found significant differences in thromboprophylaxis rates after Caesarean section, based on different guidelines.9 Anticoagulants prescribed to parturients have critical significance for anaesthetists, given the potential associated risk of neuraxial haematoma. Thus, understanding the drugs used for anticoagulation during pregnancy and their implications for anaesthetic care is key.

Anticoagulant medications used during pregnancy

For patients with an indication for anticoagulant medications during pregnancy, appropriate drugs are selected carefully by a multidisciplinary care team, including obstetricians, haematologists, cardiologists and anaesthetists. In general, unfractionated heparin (UFH) and low-molecular-weight heparins (LMWHs) are the preferred and most common anticoagulants drugs used during pregnancy given their relatively safety and shorter half-lives.

Heparin and low-molecular-weight heparins

Unfractionated heparin and LMWHs do not cross the placenta and can be safely used during pregnancy.10 Unfractionated heparin is a heterogenous mixture of high molecular weight molecules (3000–30,000 Daltons), whereas LMWHs are derived from UFH, with a molecular weight of 4000–5000 Daltons.11 An LMWH is generally preferred during pregnancy, given that they are is considered more predictable and reliable, and do not need to be dosed as frequently as UFH. The higher ratio of anti-Xa and anti-II activity of LMWH allows their use to balance effective antithrombotic activity with a lower bleeding risk.11 LMWHs also have a lower associated risk of heparin-induced thrombocytopenia given that they bind platelet factor 4 less and have fewer effects on platelet aggregation, function and activation.11 Unfractionated heparin is typically only used for thromboprophylaxis if the patient has an allergy to LMWH or has a contraindication such as renal failure.

Typical UFH doses for VTE prophylaxis in pregnancy are 5000–7500 units every 12 h in the first trimester, 7500–10,000 units every 12 h in the second trimester, and 10,000 units every 12 h in the third trimester.12 Dosing requirements increase over the course of pregnancy as blood volume, glomerular filtration rate and protein binding of heparin all increase.12 Thus, higher and more frequent doses of UFH may be required to maintain effective anticoagulation. Therapeutic UFH is used less frequently but is dosed at 10,000 units every 12 h, targeting an activated partial thromboplastin time (aPTT) of 1.5–2.5 times control 6 h after injection.12

Prophylactic LMWHs, including enoxaparin, dalteparin and tinzaparin, are typically dosed once daily; American College of Obstetricians and Gynecologists (ACOG) recommendations are based on fixed dosing, whereas Royal College of Obstetricians and Gynaecologists (RCOG) recommendations are weight-adjusted.8,12 Therapeutic LMWHs are dosed twice daily based on maternal weight.8,12

The Highlow study was a multinational randomised controlled trial of 1110 pregnant women from 70 centres in nine countries who had a previous history of VTE, comparing weight-adjusted intermediate dose LMWH with fixed low-dose LMWH for the primary outcome of a confirmed VTE event. It found that among women with a history of VTE, there was no difference in recurrence of VTE events in women receiving weight-adjusted intermediate dose LMWH compared with those receiving fixed low-dose LMWH.13 Venous thromboembolism occurred in 2% of women in the weight-adjusted intermediate dose group compared with 3% in the fixed low-dose group: relative risk 0.69 (95% confidence interval [CI] 0.32–1.47).13 Of note, patients in the Highlow study were instructed to stop their anticoagulant dose at the first signs of labour, or at 24 h before planned delivery.13 A secondary analysis of the Highlow study identified that 460 of the 1110 patients enrolled had an unplanned onset of labour, and that 19% and 39% were ineligible to receive a neuraxial procedure in the low-dose and intermediate LMWH groups, respectively.14 Such limitations must be recognised, anticipated and discussed for patients who strongly desire neuraxial analgesia or have medical indications that mean they would benefit from receiving a neuraxial technique.

Fondaparinux is a heparin-like drug that should only be used with advice from a haematologist, and reserved for patients intolerant of heparin-containing medications.8 Of particular concern is its long (17 h) half-life.15 Argatroban is another option for patients at high risk for VTE who have a history of heparin-induced thrombocytopenia.

Warfarin

Warfarin is a vitamin K antagonist less frequently used during pregnancy given its teratogenicity and ability to cross the placenta; use during the 6th to 12th weeks of pregnancy poses the greatest risk.16 However, warfarin is superior to LMWH for the prevention of mechanical heart valve thrombosis and may be selected for certain patients with mechanical heart valves after the first trimester, for whom adequate anticoagulation is critical for safety.17 Women with mechanical heart valves should have close antenatal and peripartum multidisciplinary care and counselling throughout pregnancy.17 Reversal of warfarin with either vitamin K or fresh frozen plasma may be needed at the time of delivery, given the risk of maternal retroplacental bleeding and fetal intracerebral haemorrhage near term.

Direct oral anticoagulants: oral direct thrombin inhibitors and anti-Xa inhibitors

Direct oral anticoagulants (DOACs) include direct thrombin inhibitors such as dabigatran and anti-Xa inhibitors such as apixaban and rivaroxaban. The safety profile for DOACs in pregnancy is not well established, and they are typically avoided during pregnancy given insufficient pharmacological data and the inability to exclude the risk of harmful effects on the fetus.12 All DOACs can cross into breast milk, and their use during breastfeeding is discouraged because of a relatively unknown safety profile and lack of available studies on the amount of transfer that occurs.18

Aspirin

Parturients are increasingly being treated with low-dose aspirin for prevention of pre-eclampsia. Women at risk for pre-eclampsia are recommended to take between 75 and 150 mg of aspirin daily, starting at 12 weeks' gestation, through delivery.19 Any of the following high-risk conditions are indications for aspirin prophylaxis: hypertensive disease during a previous pregnancy, chronic hypertension, chronic kidney disease, systemic lupus erythematosus, antiphospholipid syndrome, or diabetes mellitus.19 More than one of the following moderate risk factors is also considered an indication for aspirin: nulliparity, age ≥40 yrs, interpregnancy interval of >10 yrs, pre-pregnancy body mass index ≥35 kg m−2, family history of pre-eclampsia, or multiple gestation.19

Anaesthetic considerations for patients taking anticoagulants

Risk of vertebral haematoma with neuraxial block

Neuraxial analgesia provides safe and effective pain relief during labour and is the preferred form of anaesthesia during Caesarean delivery. However, complicating the provision of neuraxial anaesthesia in patients receiving anticoagulation therapies is the risk of neuraxial haematoma.20 Though the risk of neuraxial haematoma is difficult to quantitate given its rarity, the reported frequency in obstetric patients varies widely.21, 22, 23

A 5-yr multicentre US dataset with a self-selected cohort found the risk of epidural haematoma to be 1 in 251,463 (95% CI 1/46,090–1/10,142,861).21 A retrospective survey of all 85 Swedish anaesthesia departments assessing all neuraxial complications between 1990 and 1999 found two obstetric-related spinal haematomas, both in patients with HELLP (haemolysis, increased liver enzymes and low platelets) syndrome.22 After deriving a denominator of births under neuraxial anaesthesia from a Swedish birth registry, the estimated risk of spinal haematoma was found to be 1:200,000.22 An analysis of the US Nationwide Inpatient Sample, a stratified sample designed to represent all national inpatient admissions at non-federal hospitals, assessed epidural anaesthetics complicated by spinal haematoma, decompressive laminectomy, or both between 1998 and 2010.23 The authors identified 2,320,950 obstetric patients who received epidural analgesia, of whom 15 had discharge diagnoses of epidural haematoma and five of decompressive laminectomy, representing an incidence of haematoma of 1 in 154,730 (95% CI 1/93,808–1/276,243).23

A large analysis of almost 80,000 obstetric epidural blocks in the Multicenter Perioperative Outcomes Group database found no cases of epidural haematoma.24 Similarly, the Third National Audit Project of the Royal College of Anaesthetists (NAP3) found no reported spinal haematomas for 320,425 obstetric neuraxial blocks.20 A 2017 systematic review of 296 obstetric patients receiving thromboprophylaxis with either UFH or LMWH in both published studies and in the US Anesthesia Closed Claims Project Database found no cases of spinal epidural haematoma.25 This study also found that 80 of these 296 patients had neuraxial procedures performed either with thromboprophylaxis continued during labour and delivery, or after a shorter than recommended time interval between the last dose of anticoagulant and the neuraxial procedure.25 Two retrospective analyses of closed claims data from the Controlled Risk Insurance Company database encompassing data between 2005 and 2016 found no cases of spinal epidural haematoma in obstetric patients. One epidural haematoma occurred in a non-obstetric patient who had received a ventral hernia repair.26,27 A 2017 systematic review of 387 spinal haematomas among obstetric and non-obstetric cases found that haematomas occurred predominantly after epidural anaesthesia, as opposed to spinal anaesthesia, and that neurological recovery was worse if spinal decompression was delayed >12 h after initial presenting symptoms.28

Case reports describing cases of neuraxial haematoma in obstetrics remain the source of our understanding of this rare problem, and they emphasise the variable presentation of neuraxial haematoma, occurrence in the absence of any recognised haematological or iatrogenic risk factors, and challenges of timely surgical decompression to limit permanent neurological injury.29 Additionally, there have been rare reports of spontaneous spinal epidural haematoma in pregnancy.30,31

Given the significant associated morbidity, anaesthetists must remain vigilant for the diagnosis of neuraxial haematoma. Neuraxial haematoma most commonly presents with symptoms of spinal cord compression, including progressive sensory block and lower extremity motor weakness or bowel or bladder incontinence. Back pain occurs in a minority of patients, and radicular pain may or may not co-present with back pain. Safety guidelines from the Association of Anaesthetists and the Obstetric Anaesthetists' Association exist to aid in early detection of vertebral canal haematoma and timely escalation of care.32 These guidelines include recommendations for the anaesthetist to be alerted for abnormal motor block during labour or abnormal recovery from neuraxial blockade, including the inability to raise the heel off the bed against gravity during labour or the inability to perform a straight leg raise at 4 h after the last dose of local anaesthetic.32 A regional anaesthesia patient alert bracelet may also aid in early detection of abnormal neurological symptoms.33 Neurological symptoms typically evolve 24–48 h after a neuraxial procedure and warrant immediate neurological consultation and imaging, with magnetic resonance imaging being the imaging modality of choice to most sensitively and specifically diagnose neuraxial haematoma. If neuraxial haematoma is detected, emergency neurosurgical consultation and decompressive laminectomy are needed, ideally within 8 h of the onset of symptoms.34

Timing of neuraxial anaesthesia in patients taking anticoagulant medications

Recognising the increasing frequency of use and the serious morbidity associated with complications of regional anaesthesia, multiple national societies have created guidelines for the timing of neuraxial anaesthesia in pregnant patients taking anticoagulant drugs. The American Society of Regional Anesthesia (ASRA), the Society for Obstetric Anesthesia and Perinatology (SOAP), the European Society of Anaesthesiology and Intensive Care (ESAIC)/the European Society of Regional Anaesthesia and Pain Therapy (ESRA), and the Association of Anaesthetists have all developed guidelines for this situation (Table 1).35, 36, 37, 38

Table 1.

Societal recommendations for timing of neuraxial anaesthesia with commonly used anticoagulants. ACT, activated clotting time; aPTT, activated partial thromboplastin time; ASRA, American Society of Regional Anesthesia and Pain Medicine; b.d., twice daily; ESAIC/ESRA, European Society of Anaesthesiology and Intensive Care/European Society of Regional Anaesthesia & Pain Therapy; IU, international units; LMWH, low-molecular-weight heparin; SOAP, Society for Obstetric Anesthesia and Perinatology; t.d.s, three times daily; UFH, unfractionated heparin.

Anticoagulant ASRA SOAP ESAIC/ESRA Association of Anaesthetists
Thromboprophylactic
Low-dose UFH (5000 U s.c., b.d. or t.d.s.) Hold for 4–6 h OR assess coagulation status Hold for 4–6 h OR assess coagulation status Hold dose ≤200 IU kg−1 day−1 s.c. for 4 h Hold for 4 h OR assess coagulation status
Low-dose LMWH (enoxaparin ≤40 mg s.c. daily, enoxaparin 30 mg s.c. b.d., dalteparin 5000 U s.c. daily) Hold for 12 h Hold for 12 h Hold for 12 h Hold for 12 h
Intermediate-dose UFH (7500 U s.c. b.d. or 10,000 U s.c. b.d.) Hold for 12 h AND assess coagulation status Hold for 12 h AND assess coagulation status No specific recommendation No specific recommendation
Intermediate-dose LMWH No specific recommendation Insufficient data for a specific interval between 12 and 24 h No specific recommendation No specific recommendation
Aspirin (any dose) No limitations (caution with other medications that might affect clotting) No limitations (caution with other medications that might affect clotting) No limitations No limitations
Therapeutic
High-dose UFH (>10,000 U per dose or >20,000 U day−1) Hold for 24 h AND assess coagulation status Hold for 24 h AND assess coagulation status Wait until the target laboratory value (i.e. aPTT, anti-Xa, ACT) is in normal range (∼6 h if i.v. or 12 h if s.c.) No specific recommendation
I.V. UFH infusion Stop infusion for 4–6 h AND assess coagulation status Stop infusion for 4–6 h AND assess coagulation status Hold dose ≤100 IU kg−1 day−1 i.v. for 4 h Stop infusion for 4 h OR assess coagulation status
High-dose LMWH (enoxaparin 1 mg kg−1 s.c. b.d., enoxaparin 1.5 mg kg−1 s.c. daily, dalteparin 120 U kg−1 s.c. b.d., dalteparin 200 U kg−1 s.c. daily) Hold for 24 h Hold for 24 h Hold for 24 h Hold for 24 h
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Unfractionated heparin

ASRA, SOAP, and the Association of Anaesthetists recommend that for low-dose UFH thromboprophylaxis (with dosing at either 5000 units s.c. twice or three times daily), heparin should be held for 4–6 h before elective neuraxial placement OR assessment of coagulation status should occur.35,36,38 For intermediate-dose heparin (7500 units twice daily or 10,000 units twice daily), ASRA and SOAP recommend holding the dose for 12 h before elective neuraxial anaesthetic.35,36 For high-dose UFH (>10,000 units per dose or >20,000 units per day), the recommendation of ASRA and SOAP is to hold the dose 24 h before placement of neuraxial anaesthetic AND assess coagulation status.35,36 For i.v. heparin infusions, ASRA, SOAP and the Association of Anaesthetists recommend stopping the infusion for 4–6 h then assessing aPTT for coagulation status before any neuraxial anaesthetic.35,36,38 Given the risk of heparin-induced thrombocytopaenia, all patients receiving heparin for >4 days should also have a platelet count assessment before neuraxial placement.

European Society of Anaesthesiology and Intensive Care/European Society of Regional Anaesthesia & Pain Therapy guidelines are weight-based and recommend low-dose UFH (i.e. ≤200 IU kg−1 day−1 s.c. or ≤100 IU kg−1 day−1 i.v.) be held for 4 h before neuraxial block.37 For high-dose UFH, they recommend waiting until the target laboratory value (such as aPTT, anti-Xa or activated clotting time (ACT)) is in normal range (∼6 h if i.v. or 12 h if s.c.).37

For indwelling catheters, consideration of restarting anticoagulation if needed, and timing of catheter removal are also key (Table 2). Both ASRA and SOAP recommend waiting at least an hour after the neuraxial procedure or epidural catheter removal to start either s.c. or i.v. UFH.35,36 If low-dose heparin thromboprophylaxis is restarted while there is an indwelling catheter, the same timing rules listed above for neuraxial placement should be followed before catheter removal.

Table 2.

Societal recommendations after neuraxial blockade and epidural catheter removal. ASRA, American Society of Regional Anesthesia and Pain Medicine; ESAIC/ESRA, European Society of Anaesthesiology and Intensive Care/European Society of Regional Anaesthesia & Pain Therapy; IU, international units; LMWH, low-molecular-weight heparin; SOAP, Society for Obstetric Anesthesia and Perinatology; UFH, unfractionated heparin.

Anticoagulant and Action ASRA SOAP ESAIC/ESRA Association of Anaesthetists
Restarting s.c. or i.v. UFH after neuraxial placement or neuraxial catheter removal 1 h 1 h No specific recommendation 1 h
Restarting low-dose UFH thromboprophylaxis with an indwelling neuraxial catheter 4–6 h OR assess coagulation status 4–6 h OR assess coagulation status Hold dose ≤200 IU kg−1 day−1 s.c. for 4 h No specific recommendation; suggest caution
Restarting low-dose LMWH thromboprophylaxis after neuraxial placement or neuraxial catheter removal 12 h (after placement)
4 h (after removal)		 12 h after neuraxial placement and 4 h after catheter removal No specific recommendation 4 h and only 1 dose in the first 24 h after neuraxial blockade
Restarting low-dose LMWH thromboprophylaxis with an indwelling neuraxial catheter 12 h 12 h 12 h No specific recommendation; suggest caution
Restarting intermediate-dose LMWH after neuraxial placement or neuraxial catheter removal Insufficient data for a specific interval between 12 and 24 h Insufficient data for a specific interval between 12 and 24 h No specific recommendation No specific recommendation
Restarting high-dose LMWH after neuraxial placement or neuraxial catheter removal 24 h after the neuraxial placement and 4 h after catheter removal 24 h after the neuraxial placement and 4 h after catheter removal No specific recommendation 4 h; consider 24 h if block performance is traumatic
Aspirin (any dose) No limitations (caution with other medications that might affect clotting) No limitations (caution with other medications that might affect clotting) No limitations No limitations
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Low-molecular-weight heparin

Given the longer half-life of LMWH compared with UFH, ASRA, SOAP, ESAIC/ESRA and the Association of Anaesthetists all recommend holding low-dose prophylactic LMWH (which includes enoxaparin ≤40 mg s.c. once daily, enoxaparin 30 mg s.c. twice daily or dalteparin 5000 U s.c. once daily) for at least 12 h before placement of any neuraxial anaesthetic.35, 36, 37, 38 For higher-dose LMWH (including enoxaparin 1 mg kg−1 s.c. twice daily, enoxaparin 1.5 mg kg−1 s.c. once daily, dalteparin 120 U kg−1 s.c. twice daily, or dalteparin 200 U kg−1 s.c. once daily), the societies recommend holding the dose for at least 24 h before placement of a neuraxial anaesthetic.35, 36, 37, 38 For intermediate doses between low and high doses, SOAP and ASRA find insufficient data to recommend a specific time interval between 12 and 24 h before placing a neuraxial anaesthetic.35,36

Given the longer half-life of LWMH and the fact that patients at high risk for VTE are often started on LMWH after delivery, close communication with obstetric, midwifery, and nursing teams is needed to ensure that the appropriate amount of time has elapsed after epidural catheter placement and removal. The American Society of Regional Anesthesia and SOAP recommend waiting at least 12 h after the placement and at least 4 h after the catheter removal (whichever is later) before initiating low-dose LMWH thromboprophylaxis.35,36 These guidelines allow for both low-dose UFH and LMWH thromboprophylaxis in the setting of an indwelling catheter. However, medications such as non-steroidal anti-inflammatory drugs (NSAIDs) that might increase bleeding risk should be held until the epidural catheter is withdrawn if thromboprophylaxis is continued; women without an epidural catheter in situ do not need to have NSAIDs withheld even if they are receiving thromboprophylaxis after neuraxial blockade.36 For higher treatment dose LMWH, ASRA and SOAP recommend waiting at least 24 h after the neuraxial procedure and at least 4 h after epidural catheter removal before restarting LMWH.35,36 In contrast, the Association of Anaesthetists recommend 4 h elapse after catheter removal before restarting LMWH, but they advise consideration of a 24-h time period if the block performance was traumatic.38

Fondaparinux should be held for 36–42 h before neuraxial blockade or catheter removal; 6–12 h should elapse after neuraxial blockade or catheter removal before restarting the medication.37,39

Warfarin

Although warfarin is less frequently encountered in labouring patients, ASRA and ESAIC/ESRA recommend warfarin be stopped for 5 days before a neuraxial procedure, with a normal international normalised ratio (INR) level seen before proceeding.35,37 In general, pregnant women with mechanical heart valves on warfarin should switch from warfarin to twice daily LMWH by 36 weeks of pregnancy (or 2 weeks before planned birth, whichever is earlier); LMWH should be monitored with anti-Xa levels.40 Warfarin is safe for lactating patients; ASRA recommends that epidural catheters should be removed while the INR remains <1.5, ideally within 12–24 h of re-initiating warfarin.35

Oral direct thrombin inhibitors and anti-Xa inhibitors

Oral direct thrombin inhibitors and anti-Xa inhibitors are also less frequently encountered in pregnant patients. However, ASRA recommends that dabigatran be held at least 72 h before neuraxial placement in patients with normal renal function.35 Similarly, they recommend that both rivaroxaban and apixaban be stopped at least 72 h before neuraxial placement, with consideration for checking an anti-Xa concentration if <72 h have expired.35 The American Society of Regional Anesthesia recommends allowing 6 h to elapse after epidural catheter removal before restarting dabigatran or rivaroxaban.35

Aspirin

Parturients are increasingly being treated with low-dose aspirin to prevent pre-eclampsia. Given the lack of evidence that aspirin will increase the risk of neuraxial haematoma with neuraxial blocks, ASRA and ESAIC/ESRA offer no specific recommendations for timing of neuraxial procedures with respect to dosing of aspirin.35,37 However, ASRA suggests caution when other medications that might affect clotting (such as oral anticoagulants, UFH, LMWH, etc) are being taken concurrently with aspirin, or are anticipated to be started in the postpartum period.35 Similarly, SOAP specifies that NSAIDs, including aspirin, may increase the risk of bleeding with an indwelling epidural catheter and coexisting thromboprophylaxis.36

Management of patients taking anticoagulant therapy

Typically, obstetric plans to stop anticoagulant drugs before delivery are related more to the concern for neuraxial haematoma than the risk of bleeding around delivery. Thus, obstetric recommendations for stopping anticoagulants are generally in line with the recommendations listed above to allow for patients to be eligible to receive neuraxial anaesthesia. An important consideration is whether to schedule a planned induction or allow a patient taking anticoagulants to go into spontaneous labour. Problems with the use of LMWH closer to the time of delivery include its long half-life, inability to assess for its therapeutic effect, and the lack of any standard reversal agents. The transition to UFH from LMWH near the anticipated delivery date can facilitate longer anticoagulation coverage with more flexibility of reversal for neuraxial techniques and delivery. Multiple studies have shown that neuraxial anaesthesia can be successfully performed in >80% of patients taking low-dose anticoagulant medications.41,42 However, one study found a trend towards a higher rate of neuraxial analgesia use in patients undergoing scheduled induction as opposed to spontaneous labour.43 Women taking higher doses of anticoagulants are less likely to receive neuraxial blocks, as low as 37% in women on weight-adjusted intermediate-dose LMWH in the Highlow study.14

Some patients, such as those with mechanical heart valves, require their therapeutic anticoagulation to be continued during the peripartum period. Management of these patients can be challenging, given that they may receive i.v. heparin infusions intrapartum. I.V. heparin infusions are often discontinued 4–6 h before projected delivery and aPTTs monitored regularly. Close communication with obstetric and midwifery teams is required to coordinate delivery planning and timing. Neuraxial anaesthesia may be an option if laboratory studies are within normal range and anticoagulation timing guidelines have been met. Protamine should also be available for patients who experience an expedited delivery, postpartum haemorrhage, or both.

Because patients continue to be at increased risk for VTE in the immediate postpartum period, many patients who were taking anticoagulants before delivery will also need them to be restarted after delivery, often continued for 6 weeks or longer. The American College of Obstetricians and Gynecologists recommends that anticoagulation therapy be restarted no sooner than 4–6 h after vaginal delivery and no sooner than 6–12 h after Caesarean delivery; timing of the last neuraxial anaesthetic must also be taken into account.12 It should be noted that societies vary widely in their recommendations for postpartum thromboprophylaxis; one single-centre study found that in implementing ACOG postpartum guidelines, 1% of their patients would receive thromboprophylaxis after Caesarean delivery, while in implementing RCOG recommendations, 85% of patients would receive thromboprophylaxis.9 These variances underscore the importance of local multidisciplinary discussions between obstetricians and obstetric anaesthetists about anticoagulation practices as they relate to neuraxial timing, maternal safety and evolving guidelines.

Antepartum planning

Patients receiving anticoagulant medications should receive thorough antenatal counselling, not only by their obstetricians but also by an anaesthetist. The antenatal consultation provides the anaesthetist with an opportunity to ensure that the patient has a plan for bridging or stopping their anticoagulant medication before delivery, if applicable, that has been developed in concert with their obstetrician, haematologist, or both. Patients at particularly high risk for difficult airway, operative delivery, or preterm delivery may be candidates for bridging from LMWH to low-dose UFH at around 36 weeks' gestation.36 Patients who are hospitalised antenatally and require thromboprophylaxis warrant close consideration by the obstetric and anaesthesia teams as the clinical situation evolves. Such patients often have underlying morbidities, risk for imminent delivery, or both, and use of UFH affords highest flexibility for management of anaesthesia.44 At the time of the antenatal consultation, the anaesthetist should ensure that the patient understands the implications of their anticoagulant medication and the timing of a neuraxial procedure, should they desire one. The anaesthetist should discuss discontinuation of anticoagulation if the patient experiences active and regular contractions and can provide the patient with specific dates and times for withholding their anticoagulant medication before induction or scheduled delivery. In particular, the anaesthetist may also discuss the potential alternatives to neuraxial analgesia and anaesthesia, such as nitrous oxide, remifentanil patient-controlled analgesia and general anaesthesia, which may be necessary if the patient arrives in labour or for a Caesarean delivery without the appropriate amount of time having elapsed since their last dose of anticoagulant medication. Such advance planning is critical to the safe care of women taking anticoagulants.

Anaesthetic considerations for patients receiving anticoagulant medications

There may be certain situations in which a risk–benefit decision needs to be made if the patient is still in the window of inappropriate anticoagulant timing and the alternative anaesthetic choice poses significant risk to the patient. It should be emphasised that recent doses of anticoagulants is a relative contraindication to neuraxial anaesthesia, and there are circumstances in which the alternative anaesthetic may pose an even greater risk to the patient.38 For example, even for a patient who does not yet qualify for neuraxial anaesthesia based on societal anticoagulant guidelines, if an anaesthetist is facing a known difficult airway or other clinical comorbidity that would strongly favour neuraxial anaesthesia, it may be reasonable to use shared decision-making with the patient to weigh the small, but increased, risk of neuraxial haematoma with the very real possibility of a failed airway and maternal morbidity. Such discussions should always include a thorough consent process between senior clinicians and the patient, and multidisciplinary communication that includes the patient.

When the decision is made to proceed with neuraxial blockade outside of clinical guidelines, conditions should be optimised to attempt to decrease the number of needle passes, the possibility of a traumatic placement and hence the risk of neuraxial haematoma. Considerations include having the most experienced clinician perform the neuraxial technique and potentially using ultrasound. There is currently little evidence for the use of point-of-care anticoagulation testing to assess suitability for neuraxial anaesthesia. In addition, close neurological follow-up should be arranged for these patients, including ensuring resolution of motor block after delivery and neurological examination of the lower extremities. If patients are receiving neuraxial labour analgesia, using low concentration local anaesthetics may limit the extent of motor block during labour, to allow for concurrent assessment of epidural haematoma.

Conclusions

Venous thromboprophylaxis is an important component of antenatal care for women at increased risk for VTE. However, there are many critical obstetric and anaesthetic considerations for these high-risk parturients. Pregnant patients taking anticoagulant drugs should receive thorough antenatal counselling with obstetricians, obstetric anaesthetists and haematologists (if applicable). In addition, close communication between the obstetric and anaesthesia teams regarding any key changes in the patient's antenatal course, especially if there is concern for expedited delivery, is critical. Such communication between the obstetricians and anaesthetists is vital to ensure that the anaesthesia team can make timely modifications to their plans and communicate these to the patient in the event of acute changes in their clinical status that might affect delivery. In addition, some discussions related to anticoagulation planning may need to involve other specialties, such as haematology or cardiology. Such counselling and multidisciplinary planning ensures that patients and healthcare providers understand the implications of anticoagulant medications for neuraxial anaesthesia, and can facilitate the safest plans for delivery.

Declaration of interests

The authors declare that they have no conflicts of interest.

MCQs

The associated MCQs (to support CME/CPD activity) will be accessible at www.bjaed.org/cme/home by subscribers to BJA Education.

Biographies

Sharon Reale MD is an obstetric anaesthesiologist at Brigham and Women's Hospital. She is the fellowship program director for the obstetric anesthesia division. Her research focuses on leveraging large databases to study maternal morbidity and mortality, including rare comorbidities and outcomes.

Michaela Farber MD MS is an obstetric anaesthesiologist at Brigham and Women's Hospital. She is the obstetric anesthesia division chief. Her research focuses on postpartum haemorrhage and coagulation.

Matrix codes: 1A02, 2B01, 3B00

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