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Am J Perinatol
DOI: 10.1055/a-2753-9286
Original Article

Low Molecular Weight Heparin Thromboprophylaxis or No Treatment following Cesarean Delivery: A Pilot Randomized Controlled Trial

Authors

  • Ann M. Bruno

    1   Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of Utah Health, Salt Lake City, Utah, United States

  • Amanda A. Allshouse

    1   Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of Utah Health, Salt Lake City, Utah, United States

  • D W. Branch

    1   Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of Utah Health, Salt Lake City, Utah, United States

  • Robert M. Silver

    1   Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of Utah Health, Salt Lake City, Utah, United States

  • Torri D. Metz

    1   Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of Utah Health, Salt Lake City, Utah, United States

Funding Information A.M.B. received support from the Eunice Kennedy Shriver National Institute of Child Health and Human Development Women's Reproductive Health Research (WRHR) K12 (grant no.: 5K12HD085816) during the completion of this research. The research reported in this publication was also supported in part by the National Center for Advancing Translational Sciences of the National Institutes of Health under Award Numbers, UL1TR002538 and UM1TR004409.
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Abstract

Objective

This study aimed to evaluate the feasibility of randomizing patients to weight-based low molecular weight heparin (LMWH) versus no pharmacologic thromboprophylaxis following cesarean delivery (CD).

Study Design

Single-center, open-label pilot randomized controlled trial of individuals aged 18+ undergoing CD at the University of Utah Health from November 2023 to June 2024. Those with a contraindication to anticoagulation, a plan for therapeutic anticoagulation, or considered at highest risk for postpartum venous thromboembolism (VTE; i.e., undergoing cesarean-hysterectomy, high-risk thrombophilia, personal history of thromboembolism) were excluded. Enrolled individuals were randomized in a 1:1 ratio utilizing block randomization with randomly varying block sizes to receive weight-based LMWH for 14 days or no pharmacologic thromboprophylaxis. The primary outcome was feasibility, defined as ≥35% enrollment of eligible individuals and retention of ≥85% of enrolled individuals through all study procedures. Secondary feasibility outcomes included the number of eligible patients per month, approach rate, enrollment rate, and retention rate. Additional outcomes included VTE, wound hematoma, patient-reported symptoms, or a bleeding complication within 6 weeks postpartum. Baseline characteristics were compared between those approached and enrolled and those not enrolled. The proportion meeting each of the outcomes was reported with 95% confidence intervals (CI).

Results

Over the 6-month study period, 694 patients were screened and found eligible for an average of 106 eligible patients per month. There were 611 patients approached (88%, 95% CI: 85.6–90.5), of which 64 enrolled (10.5%, 95% CI: 8–12.9), and 61 participants were retained through all study procedures (95.3%, 95% CI: 90–100). Thus, the overall primary outcome feasibility parameters were not met. Among the 64 individuals enrolled and randomized, the mean age was 31.0 years (standard deviation: 5.5 years), and the majority were non-Hispanic White (56%). Baseline characteristics were similar between those who were approached and enrolled compared with those not enrolled. There were no differences in additional clinical outcomes (VTE, wound hematoma, patient-reported symptoms, or bleeding complications) by prophylaxis group.

Conclusion

In this pilot trial, individual patient randomization to weight-based LMWH or no pharmacologic thromboprophylaxis after CD was not feasible due to low enrollment rates. Future trials addressing postpartum thromboembolism prevention should consider alternative study designs.

Key Points

  • Individual patient randomization to enoxaparin or no therapy after CD was not feasible.

  • The approach rate, enrollment rate, and retention rate were 88, 11, and 95%, respectively, in this single-center pilot.

  • Future prospective studies may need to consider alternative designs.

Keywords

enoxaparin - feasibility - pilot trial - thromboprophylaxis - VTE

Note

The content is solely the responsibility of the authors and does not necessarily represent the views of the National Institutes of Health.


Supplementary Material



Publication History

Received: 08 February 2025

Accepted: 23 November 2025

Accepted Manuscript online:
25 November 2025

Article published online:
05 December 2025

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