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further evaluation of this technique is required before its widespread incorporation into diagnostic algorithms. For MRA, the long-term effects of gadolinium contrast on the foetus are not known. In nonpregnant patients, technically inadequate images are frequently obtained and the rate of inconclusive scan results is high.140 Therefore, use of this technique for diagnosing or ruling out PE during pregnancy cannot be recommended at present. Conventional pulmonary angiography involves significantly higher radiation exposure of the foetus (2.23.7 mSv) and should be avoided during pregnancy.400 Overdiagnosis of PE is a potential pitfall that can have significant, lifelong implications for a pregnant woman, including the risk of bleeding at the time of delivery, the withholding of oestrogen contraception, and the requirement for thromboprophylaxis during future pregnancies. Consequently, avoiding PE overdiagnosis in pregnancy is as important as not missing a PE diagnosis.

9.3 Treatment of pulmonary embolism in

pregnancy LMWH is the treatment of choice for PE during pregnancy.384 In contrast to VKAs and NOACs, LMWH does not cross the placenta, and consequently does not confer a risk of foetal haemorrhage or teratogenicity. Moreover, while UFH is also safe in pregnancy, LMWH has more predictable pharmacokinetics and a more favourable risk profile.408411 Although no RCT has evaluated the optimal dose of LMWH for the treatment of PE during pregnancy, currently published data favour similar dosing to non-pregnant patients, either with o.d. or b.i.d. regimens based on early pregnancy weight.408,410 For the majority of patients receiving LMWH treatment for PE during pregnancy,412,413 it remains uncertain whether using serial measurements of plasma anti-activated coagulation factor X activity to guide dosing may be of clinical benefit. It is important to bear in mind that: (i) LMWH has a predictable pharmacokinetic profile, (ii) data on optimal anti-activated coagulation factor levels are lacking, and (iii) the assay itself has limitations.414 In addition, there are no solid data on the clinical benefit vs. harm of frequent, weight-based dose adjustments of LMWH during pregnancy. Thus, anti-activated coagulation factor X monitoring may be reserved for specific high-risk circumstances such as recurrent VTE, renal impairment, and extremes of body weight.

The use of UFH has been associated with heparin-induced thrombocytopenia and bone loss. It remains uncertain whether, and to what extent, the risk of bone loss is increased with LMWH use. In a recent observational cohort study, in which bone mineral density was measured by dual-energy X-ray absorptiometry 47 years after the last delivery in 152 women (92 of whom received prolonged LMWH during pregnancy), lumbar spine bone mineral density was similar in LWMH-treated women and controls following adjustment for potential confounders. No osteoporosis or osteoporotic fractures were reported.415 Fondaparinux may be considered if there is an allergy or adverse response to LMWH, although solid data are lacking and minor transplacental passage has been demonstrated.416 VKAs cross the placenta and are associated with a well-defined embryopathy during the first trimester. Administration of VKAs in the third trimester can result in foetal and neonatal haemorrhage, as well as placental abruption. Warfarin may be associated with central nervous system anomalies in the foetus throughout pregnancy. NOACs are contraindicated in pregnant patients.417 The management of labour and delivery requires particular attention. In women receiving therapeutic LMWH, strong consideration should be given to planned delivery in collaboration with the multidisciplinary team to avoid the risk of spontaneous labour while fully anticoagulated. The incidence of spinal haematoma after regional anaesthesia is unknown in pregnant women under anticoagulation treatment. If regional analgesia is considered for a woman receiving therapeutic LMWH, >_24 h should have elapsed since the last LMWH dose before insertion of a spinal or epidural needle (assuming normal renal function and including risk assessment at extremes of body weight). In high-risk situations, for example in patients with recent PE, it is recommended that LMWH be converted to UFH >_36 h prior to delivery. The UFH infusion should be stopped 4 - 6 h prior to anticipated delivery and the activated partial thromboplastin time should be normal (i.e. not prolonged) prior to regional anaesthesia.418 Data are limited on the optimal timing of post-partum reinitiation of LMWH.419,420 Timing will depend upon the mode of delivery and an assessment of the thrombotic vs. bleeding risk by a multidisciplinary team. LMWH should not be given for >_4 h after removal of the epidural catheter; the decision on timing and dose should consider whether the epidural insertion was traumatic, and take into account the risk profile of the woman. For example, an interim dose of a prophylactic LMWH dose may be considered post-operatively (after caesarean section), once at least 4 h have elapsed since epidural catheter removal, and allowing for an interval of >_812 h between the prophylactic and the next therapeutic dose. Close collaboration between the obstetrician, the anaesthesiologist, and the attending physician is recommended. Anticoagulant treatment should be administered for >_6 weeks after delivery and with a minimum overall treatment duration of 3 months. LMWH and warfarin can be given to breastfeeding mothers; the use of NOACs is not recommended.417

Table 12 Estimated amounts of radiation absorbed in procedures used to diagnose pulmonary embolism (based on various references385,392–398)

Test Estimated foetal radiation exposure (mGy)a Estimated maternal radiation exposure to breast tissue (mGy)a Chest X-ray <0.01 <0.1 Perfusion lung scan with

technetium-99mlabelled albumin Low dose: 40 MBq High dose: 200 MBq 0.020.20 0.200.60 0.160.5 1.2 Ventilation lung scan 0.100.30 <0.01 CTPA 0.050.5 310 CTPA = computed tomography pulmonary angiography; mGy = milligray; MBq = megabecquerel; PE = pulmonary embolism. aIn this section, absorbed radiation dose is expressed in mGy to reflect the radiation exposure to single organs, or the foetus, as a result of various diagnostic techniques. Compare with Table 6, in which effective radiation dose is expressed in millisieverts to reflect the effective doses of all organs that have been exposed. Downloaded from academic.oup.com/eurheartj/article/41/4/543/5556136 by guest on 07 October 2026