Case Study
A 36-year-old gravida 1, para 2 parturient was booked for an elective cesarean delivery at 38 weeks’ gestation. Body mass index (BMI) at her booking appointment was 29 kg/m2. Her previous pregnancy resulted in an emergency cesarean delivery following prolonged fetal bradycardia. She developed chorioamnionitis postoperatively requiring 7-day in-patient IV antibiotic therapy.
At 27 weeks’ gestation, following recent history of long-haul travel, she developed an acutely painful and swollen left calf. Duplex ultrasonography demonstrated a left popliteal deep vein thrombosis (DVT). Further investigation revealed no other medical cause for the thrombosis, and the patient was diagnosed with pregnancy-associated venous thromboembolism (VTE). Self-administered subcutaneous low-molecular-weight heparin (LMWH) therapy was subsequently started for the remainder of her pregnancy.
On preoperative visit, she was visibly distressed and anxious to leave the hospital soon after her procedure. She confirmed that she had no other medical history, medications, or allergies. Preoperative hematology investigations revealed normal hemoglobin (112 g/liter) and clotting profile. Her last therapeutic LMWH injection was 24 hours previously.
The anesthetist sited a 16-gauge IV cannula and performed a combined spinal-epidural, administering intrathecal heavy bupivacaine with opioid. No complications were encountered during anesthesia. She received 2 liters of warmed compound sodium lactate solution intraoperatively, and the estimated blood loss was approximately 1.4 liters. Near-patient testing (venous blood gas sample) revealed a postoperative hemoglobin level of 87 g/liter.
Following surgery, the patient remained anxious to go home as soon as possible and avoid the prolonged admission that she had previously experienced.
Key Points
If a parturient has had an antenatal DVT, she remains at high risk of thrombotic events after cesarean delivery.
The need for prompt therapeutic anticoagulation postoperatively must be balanced against risks of bleeding and signs of blood loss.
Patient choices must be accommodated if medically safe to do so.
Discussion
Venous thromboembolism, encompassing deep vein thrombosis (DVT) and pulmonary embolism (PE), is the leading cause of direct maternal deaths within the United Kingdom, with an estimated mortality of 1.08 per 100,000 pregnancies.1 VTE is estimated to affect 0.5–3 of every 1,000 pregnancies.2 Prompt diagnosis and early treatment are vital to improve VTE-related mortality within this patient cohort.3
Pregnancy itself is a significant risk factor for development of VTE, with parturients 10 times more likely to develop VTE than age-matched nonpregnant women.3 The most common time for a parturient to develop VTE is the puerperium (6 weeks following delivery).3 Table 48.1 summarizes the risk factors for development of VTE in pregnancy. The patient in this Case Study has multiple risk factors, including: advanced maternal age, high BMI, and recent immobilization, and is therefore deemed high risk of developing VTE.
Diagnosis of VTE in Pregnancy
The Royal College of Obstetricians and Gynaecologists (RCOG) recognizes that due to the presence of limited evidence surrounding management of VTE in pregnancy, recommendations are often extrapolated from nonpregnant women. Therefore, the RCOG provides suggestions from which it is recommended that each hospital develop its own policies.
Diagnosis of Deep Vein Thrombosis
For diagnosis of DVT, compression duplex ultrasound is considered to be the “gold standard” investigation. This should be repeated after 7 days in the event of an inconclusive result with ongoing clinical suspicion.
Diagnosis of Pulmonary Embolism
All possible cases of PE should be investigated primarily with a chest radiograph because this can diagnose other common causes of dyspnea while minimizing radiation dose to the fetus. Follow-up investigations include either a ventilation-perfusion (VQ) scan or computerized tomographic pulmonary angiography (CTPA), with the choice of investigation depending on local policy. D-dimer levels are usually elevated by term and during the postnatal period; therefore, it is not deemed to be a useful investigation during pregnancy.4
The British Thoracic Society recommends CTPA as a first-line investigation in the nonpregnant population for suspected PE. However, during pregnancy, maternal breast tissue becomes more sensitive to radiation. Following a CTPA, the lifetime risk of breast cancer increases by 13.6 percent within the pregnant population.5 CTPA does, however, expose the fetus to a lower dose of radiation than a VQ scan and can also accurately diagnose other respiratory conditions. The RCOG recommends avoiding CTPA, particularly in the presence of risk factors for breast cancer, including familial history and previous CTPA.
VQ scans do not pose the same risks to maternal breast tissue as CTPA, and these risks can be further mitigated by omitting the ventilation aspect of the scan. VQ scans do, however, subject the fetus to a higher radiation dose than CTPA. Risk-benefit analysis must be considered prior to exposing the fetus to any radiation because it is associated with prenatal death, intrauterine growth restriction, organ malformation, mental retardation, and childhood cancer.6 Despite these risks, VQ scan remains the preferred investigation for PE in most units in view of the substantial maternal risk of breast cancer associated with CTPA.7
Management of VTE in Pregnancy
As pregnant women are at high risk of VTE, it is recommended that all suspected cases of VTE be treated empirically with LMWH until definitive investigation. Peripartum VTE investigation and management strategies are summarized in Table 48.2.
| First trimester | Second trimester | Third trimester | Delivery to 3 days after deliver | Three days to 6 weeks after birth | More than 6 weeks after birth | |
|---|---|---|---|---|---|---|
| Investigation |
|
| ||||
| Treatment | Enoxaparina or dalteparinc | |||||
| Duration of treatment | For the duration of pregnancy, 6 weeks after birth, and for at least 3 months |
| ||||
Note: WLR = warfarin loading regime.
a Enoxaparin 1 mg/kg twice daily.
b Enoxaparin 1.5 mg/kg once daily.
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