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A more selective risk-stratified approach to postpartum enoxaparin (Lovenox) thromboprophylaxis for venous thromboembolism (VTE) was linked to reduced rates of wound hematomas without increasing the rate of VTE, according to a retrospective observational study conducted at a large referral center.

Among over 17,000 patients, the more selective enoxaparin protocol was associated with a reduction in wound hematomas compared with the original standard protocol (0.3% vs 0.7%; adjusted OR 0.38, 95% CI 0.21-0.67), reported a group led by Macie Champion, MD, of the University of Alabama at Birmingham (UAB).

This benefit was driven largely by a 50% lower rate of superficial wound hematomas (0.3% vs 0.6%, respectively; aOR 0.43, 95% CI 0.24-0.75), they noted in .

The selective protocol was also associated with fewer wound complications of any kind (1.4% vs 2.0%; aOR 0.66, 95% CI 0.50-0.86).

Meanwhile, the institution saw no change in incidence of VTE -- namely, deep venous thrombosis or pulmonary thromboembolism, or any other VTE -- between the original and more selective protocols (0.008% vs 0.0014%, aOR 0.40, 95% CI 0.12-1.36).

"Given the rarity of VTE, which would necessitate a large randomized trial that is likely infeasible, future studies should continue to evaluate chemoprophylaxis guidelines to determine the utility and safety of routine use of heparin-based thromboprophylaxis, even in populations at higher risk of postpartum VTE," Champion and colleagues wrote.

They explained that UAB historically followed no pregnancy-related anticoagulation guidelines until 2016, when the institution adopted a risk-stratified enoxaparin protocol based on expert opinion and observational data and recommended by organizations including the American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine.

Like other groups, the UAB researchers observed an increase in wound hematomas using that protocol.

In 2021, the hospital implemented a more selective risk-stratified approach, which was compared against the original 2016 protocol in the present report.

The more selective protocol consists of giving enoxaparin to patients if they have a history of VTE or nephrotic syndrome and at least three additional risk factors. Other changes from the older protocol included:

• Removal of preeclampsia, ages 40 and older, and thrombophilia as risk factors
• Downgrading pre-pregnancy BMI ≥40 to a secondary risk factor
• Making sepsis a risk factor instead of any major infection
• Raising the bar for systemic lupus erythematosus patients to those already taking at least two medications for it

With these stricter criteria, enoxaparin administration fell from 16% to 8%.

This study was based on 17,489 pregnant women who delivered at UAB during two periods, one while the original protocol was in place (2016-2018; 71%) and the other after implementation of the more selective risk-stratified approach (2021-2023; 29%).

Patients receiving outpatient anticoagulation for active VTE or considered high risk for VTE during pregnancy were excluded.

Between the two study groups, patients in the more selective protocol group were older (28.5 vs 27.7 years), less likely to have government-funded insurance (59% vs 65%), had a higher BMI (31 vs 30), were more likely to use aspirin (23% vs 18%), and were more likely to be diagnosed with preeclampsia (21% vs 16%).

The study's primary analysis focused on the incidence of wound hematomas occurring from after delivery through 6 weeks postpartum. The researchers used multivariable logistic regression for their analysis, and findings were confirmed with propensity-matched analyses.

Notably, women who underwent cesarean delivery had a disproportionately low risk of wound hematomas with the more selective protocol (aOR 0.22, 95% CI 0.11-0.46).

Nevertheless, Champion and team cautioned that they could not fully address confounding given the study's retrospective design. Whether the results are generalizable to other institutions is also unclear.

"In addition, future studies should evaluate the safety of newer oral anticoagulants in the postpartum period, considering lactation, as potential alternatives to heparin-based thromboprophylaxis," they wrote.

The primary results from this study had been reported earlier this year at the Society for Maternal-Fetal Medicine's annual meeting.

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