Options for Peripartum Anticoagulation in Areas Affected by Shortage of Unfractionated Heparin

  • March 2020

(Reaffirmed October 2022)

This Practice Advisory is endorsed by the Society for Maternal-Fetal Medicine (SMFM) and the Society for Obstetric Anesthesia and Perinatology (SOAP). This Practice Advisory is supported by the American Society of Anesthesiologists* (ASA). 

Authors: Meredith L. Birsner, MD; Mark Turrentine, MD; Christian M. Pettker, MD; Anjali J. Kaimal, MD, MS; Kathleen Brookfield, MD; and SOAP-liaison Lisa R. Leffert, MD. 

The American College of Obstetricians and Gynecologists is aware of recent shortages or temporary periods of reduced access to unfractionated heparin. A potential risk of a global shortage of the supply of active pharmaceutical ingredients used for heparin products is being monitored on an international level 1. Baxter Healthcare first reported to the U.S. Food and Drug Administration in November 2017 shortages of heparin sodium 2,000 international units/L in 0.9% weight/volume sodium chloride intravenous infusion, heparin sodium 2,000 USP units in 1,000 mL, and heparin sodium 1,000 USP units in 500 mL  2. The purpose of this practice advisory is to review options for anticoagulation in late gestation for practitioners in areas affected by a heparin shortage. 

In some cases, obstetricians, in conjunction with hematologists and maternal–fetal medicine subspecialists, have transitioned pregnant women on anticoagulation from low-molecular-weight heparin (LMWH) regimens to unfractionated heparin (UFH) at or near 36 weeks of gestation. The purpose of conversion to unfractionated heparin has less to do with any risk of maternal bleeding at the time of delivery, than with the low risk of an epidural or spinal hematoma with regional anesthesia. Although this practice is not required, it is sometimes used to facilitate the safe use of neuraxial anesthesia 3, given the longer half-life of LMWH compared with UFH and greater ease of reversal of UFH by protamine sulfate, although protamine is uncommonly required. Indeed, the ACOG Practice Bulletin on Thromboembolism in Pregnancy states “women receiving anticoagulation therapy may be converted from low-molecular weight heparin to the shorter half-life unfractionated heparin in anticipation of delivery, depending on the institution” 4. This is consistent with recommendations from the Society of Obstetric Anesthesia and Perinatology (SOAP) consensus statement on the Anesthetic Management of Pregnant Women Receiving Thromboprophylaxis 3 and the 2018 American Society of Hematology (ASH) 2018 guidelines for management of venous thromboembolism in the context of pregnancy 5

An alternative option for women on either prophylactic or adjusted-dose LMWH may be to stop anticoagulation and induce labor within 12 to 24 hours respectively, if clinically appropriate 4.  The implications of these recommendations vary based on the pregnant woman’s degree of venous thromboembolism (VTE) risk, anticoagulant dose (low-dose prophylaxis versus intermediate- or adjusted-dose LMWH), preferences and plans regarding mode of delivery and desire for spontaneous labor, and the clinical importance of performing neuraxial blockade (epidural, spinal, combined spinal-epidural) for labor analgesia or cesarean anesthesia.  The following are some suggested recommendations based on clinical circumstances:

  • For planned cesarean, the final dose of intermediate- or adjusted-dose LMWH should be administered no sooner than 24 hours before surgery in which neuraxial anesthesia is planned; this includes doses of enoxaparin above 40 mg SQ daily or above 30 mg subcutaneously twice daily 3. For planned cesarean, the final dose of prophylactic (low-dose) LMWH (enoxaparin 40 mg subcutaneously daily or 30 mg subcutaneously twice daily) should be administered no sooner than 12 hours before surgery in which neuraxial anesthesia is planned 3. Pneumatic compression devices, when not contraindicated, should be maintained throughout surgery and postpartum until the patient is fully ambulatory. Anticoagulation should be resumed postpartum in accordance with anesthesiology input regarding catheter removal, with consideration of any intraoperative complications such as hemorrhage.   
  • For other circumstances, planned delivery would involve induction of labor, in accordance with local obstetric practice and protocols. Women who prefer to await spontaneous labor can generally receive neuraxial anesthesia 12 hours after low-dose prophylactic LMWH and 24 hours after intermediate- or adjusted-dose LMWH 3
  • If a woman using LMWH who desires neuraxial anesthesia enters spontaneous labor and the requisite safe time interval has not yet passed, alternative pain management approaches should be considered 6.

These suggestions should be adapted for patients with acute medical or pregnancy complications that might complicate the planning or timing of delivery. For instance, the management of antepartum patients who require anticoagulation who are also admitted with conditions that predispose to risk of urgent delivery should be considered carefully, and there may be cases where the rationed use of unfractionated heparin may be necessary. This emphasizes the importance of coordinating the general approach to heparin use in a hospital with pharmacists and obstetric anesthesiologists who have sufficient lead time before labor or planned delivery.

The American College of Obstetricians and Gynecologists emphasizes the importance of multidisciplinary collaboration with subspecialties such as anesthesiology and maternal-fetal medicine, as well as the concept of shared-decision making and patient autonomy regarding delivery planning. Patients should be educated to consult with their obstetric care clinicians before taking their next anticoagulant dose if they suspect they are in labor or if they have rupture of membranes, vaginal bleeding, or both. Gestational age should be an important consideration in decision making surrounding delivery and, if medical management of anticoagulation is the isolated factor driving delivery planning, delivery for that indication alone need not occur before 39 weeks of gestation unless extenuating circumstances exist.

Please contact [email protected] with any questions.

*Since this document has neither been presented to nor approved by either the ASA Board of Directors or House of Delegates, it is not an official or approved statement or policy of the Society. Variances from the recommendations contained in the document may be acceptable based on the judgment of the responsible anesthesiologist.


  1. Vilanova E, Tovar AMF, Mourao PAS. Imminent risk of a global shortage of heparin caused by the African swine fever afflicting the Chinese pig herd. J Thromb Haemost 2019;17:254-6. Available at: Retrieved February 28, 2020.
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  2. U.S. Food and Drug Administration. Heparin sodium and sodium chloride 0.9% injection. In: FDA drug shortages: current and resolved drug shortages and discontinuations reported to FDA. Silver Spring, MD: FDA; 2020. Available at: Retrieved February 28, 2020.
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  3. Leffert L, Butwick A, Carvalho B, Arendt K, Bates SM, Friedman A, et al. The Society for Obstetric Anesthesia and Perinatology consensus statement on the anesthetic management of pregnant and postpartum women receiving thromboprophylaxis or higher dose anticoagulants. Members of the SOAP VTE Taskforce. Anesth Analg 2018;126:928-44. Available at: Retrieved February 28, 2020.
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  4. Thromboembolism in pregnancy. ACOG Practice Bulletin No. 196. American College of Obstetricians and Gynecologists [published erratum appears in Obstet Gynecol 2018;132:1068]. Obstet Gynecol 2018;132:e1–17. Available at: Retrieved February 28, 2020.
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  5. Bates SM, Rajasekhar A, Middeldorp S, McLintock C, Rodger MA, James AH, et al. American Society of Hematology 2018 guidelines for management of venous thromboembolism: venous thromboembolism in the context of pregnancy. Blood Adv 2018;2:3317-59. Available at: Retrieved February 28, 2020.
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  6. Approaches to limit intervention during labor and birth. ACOG Committee Opinion No. 766. American College of Obstetricians and Gynecologists. Obstet Gynecol 2019;133:e164-73. Available at: Retrieved February 28, 2020.
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