How to Navigate the Challenges of Anticoagulant Therapy in Pregnant Women − A Case Study

First Pregnancy

A 36-year-old woman visits the cardiac surgery outpatient clinic to plan a pregnancy. At 22, she underwent mitral valve replacement with a mechanical valve and surgery for an atrial septal defect. Since then, she has been on warfarin. She is currently 167 cm tall and weighs 58.5 kg. An initial examination included a chest X-ray showing cardiomegaly, an EKG revealing atrial fibrillation and right bundle branch block, and echocardiography confirming left atrial hypertrophy, mild aortic regurgitation, and good function of the artificial valve. Her measured INR was 2.34, within the therapeutic range. The plan was to continue anticoagulation with warfarin, switching to enoxaparin upon confirmation of pregnancy.

After a positive pregnancy test, a single fetus at 5 weeks was confirmed. A follow-up echocardiographic examination showed a left ventricular ejection fraction (LVEF) of 59%, pressure gradient of 5.16 mmHg, and V_mean of 1.04 m/s. According to the plan, the patient discontinued warfarin and began subcutaneous administration of 60 mg enoxaparin twice daily (1 mg/kg/dose) with a target anti-Xa level between 0.3−0.7 IU/ml. The anti-Xa level was monitored monthly, as were echocardiography, both remaining stable. At 20 weeks of pregnancy, the patient experienced a mild bleeding episode that did not require a reduction in the enoxaparin dose. Prenatal ultrasound examinations were conducted monthly up to 30 weeks, then bi-weekly and weekly from the 36th week onwards, all with physiological findings.

After consulting with a gynecologist, the decision was made for a vaginal delivery to reduce the risk of blood loss associated with cesarean section. Upon admission to the hospital, enoxaparin was replaced with unfractionated heparin, which was discontinued 6 hours before delivery and restarted after ruling out postpartum bleeding. The birth took place at 37+5 weeks of gestation, and the baby was healthy. The following day, warfarin was reintroduced along with enoxaparin, which was discontinued upon reaching an INR of 1.8. A postpartum echocardiogram showed favorable valve function measurements. On the 10th day postpartum, the patient was admitted for postpartum hemorrhage, requiring the suspension of warfarin and a blood transfusion. After observation, she was discharged without complications.

Once and Done? No Way!

The approach was the same for her second pregnancy, which followed a year and a half later. At 18 weeks of pregnancy, the patient again experienced a bleeding episode, which this time required a temporary cessation of enoxaparin. The second child was delivered vaginally at 38+3 weeks of gestation. The postpartum echocardiographic examination again showed favorable heart and valve function. After the birth, warfarin was reintroduced.

Which Anticoagulant to Choose?

Although warfarinization is beneficial for patients with artificial valves, using this medication during pregnancy is inappropriate due to the high risk of congenital malformations. Pregnancy generally represents a pro-coagulant state, and the risk of thrombotic events is even higher in patients with atrial fibrillation, especially those with an implanted artificial valve.

Although many modern anticoagulants are available, data on their use during pregnancy is very limited. In this case, enoxaparin was chosen based on its reported safety during pregnancy. Available expert sources are divided on the recommended anti-Xa levels. The attending physicians in this case study opted for a range of 0.3−0.7 IU/ml instead of the recommended 0.8−1.2 IU/ml (for the Asian population). The chosen anticoagulant therapy successfully prevented thrombotic events and maintained good artificial valve function in the patient, who successfully delivered 2 children.

Based on this case study, it can be concluded that enoxaparin may be safely used in pregnant women with atrial fibrillation and mechanical valves as an alternative to warfarin, with careful monitoring.

(dape)

Source: Lee Y. S., Kim J. S. Enoxaparin as an anticoagulant in a multipara with a mechanical mitral valve: a case report. J Chest Surg 2023; 56 (6): 452–455, doi: 10.5090/jcs.23.031.