As a professional pharmacist, you will hear more about PREVENTING venous thromboembolism (VTE) during pregnancy due to new expert guidance from American College of Obstetricians and Gynecologists (ACOG) and others. VTE accounts for about 10% of maternal deaths in the United States. Watch for women who are at risk during pregnancy and postpartum, such as those with a clotting disorder or previous VTE.
In most cases, use PROPHYLACTIC low-molecular-weight heparin (LMWH) doses, such as enoxaparin 40 mg daily or 40 mg BID in obese women. But give TREATMENT doses of LMWH (enoxaparin 1 mg/kg BID, etc) in the highest-risk women, such as those with multiple prior clots. Dose LMWH based on actual weight when it's started. It's not usually necessary to increase the dose as pregnancy weight goes up. Don't routinely check anti-Xa levels, there's no good evidence that this monitoring improves LMWH efficacy or safety in pregnancy.
Continue LMWH at the same dose postpartum, usually for 6 weeks. It's okay in nursing moms and doesn't accumulate in breast milk. Don't think of oral medications as an alternative. Direct oral anticoagulants (Eliquis, etc) haven't been studied as much in pregnancy or breastfeeding and aspirin alone isn't effective for preventing VTE. Generally avoid warfarin in pregnancy. It's linked to birth defects and it's tricky to stabilize the dose short-term. Don't suggest compression stockings. There's not much evidence they prevent clots and they're cumbersome to wear, especially in pregnancy.
| Table (1). Use of heparins during pregnancy | ||
|---|---|---|
| Heparin | Dose level | Dosage |
| LMW heparin | Prophylactic | Enoxaparin 40 mg SC once daily |
| Dalteparin 5000 units SC once daily | ||
| Intermediate | Enoxaparin 40 mg SC once daily, increase as pregnancy progresses to 1 mg/kg once daily | |
| Dalteparin 5000 units once daily, increase as pregnancy progresses to 100 units/kg once daily | ||
| Therapeutic | Enoxaparin 1 mg/kg every 12 hours | |
| Dalteparin 100 units/kg every 12 hours | ||
| Unfractionated heparin | Prophylactic | 5000 units SC twice daily |
| Intermediate | First trimester: 5000 to 7500 units every 12 hours | |
| Second trimester: 7500 to 10,000 units every 12 hours | ||
| Third trimester: 10,000 units every 12 hours | ||
| Therapeutic | Dose every 12 hours to keep aPTT at 1.5 to 2.5 times control or patient's baseline six hours after dose | |
| LMW: low molecular weight; SC: subcutaneously; aPTT: activated partial thromboplastin time. | ||
REFERENCES
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DʼAlton ME, Friedman AM, Smiley RM, Montgomery DM, Paidas MJ, DʼOria R, Frost JL, Hameed AB, Karsnitz D, Levy BS, Clark SL. National Partnership for Maternal Safety: Consensus Bundle on Venous Thromboembolism. Obstet Gynecol. 2016 Oct;128(4):688-98. Available at: https://journals.lww.com/greenjournal/Fulltext/2016/10000/National_Partnership_for_Maternal_Safety_.3.aspx
Bates SM, Greer IA, Middeldorp S, Veenstra DL, Prabulos AM, Vandvik PO. VTE, thrombophilia, antithrombotic therapy, and pregnancy: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest. 2012 Feb;141(2 Suppl):e691S-e736S. Available at: https://journal.chestnet.org/article/S0012-3692(12)60136-6/fulltext
James AH. Venous thromboembolism in pregnancy. Arterioscler Thromb Vasc Biol. 2009 Mar;29(3):326-31. Available at: https://www.ahajournals.org/doi/10.1161/ATVBAHA.109.184127?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub%20%200pubmed