A Retrospective Analysis to Evaluate the Impact of Obesity on Therapeutic Enoxaparin Dosing in Pregnancy

Abstract

Background:

In the United States, standard enoxaparin treatment dosing in pregnant patients is 1 mg/kg subcutaneously twice daily. For nonpregnant patients with obesity (body mass index (BMI) ≥30 kg/m²), literature supports empiric dose reductions to 0.8 mg/kg subcutaneously twice daily.

Objective:

To investigate whether pregnant patients with obesity require empiric enoxaparin treatment dose adjustments compared to pregnant patients without obesity.

Methods:

This retrospective chart review included pregnant adults who received therapeutic enoxaparin and had appropriately timed low-molecular-weight heparin (LMWH) anti-factor Xa levels. The primary endpoint compared initial LMWH anti-factor Xa levels between patients with and without obesity. Secondary endpoints included the frequency and extent of enoxaparin dose adjustments by BMI, among those with nontherapeutic initial levels. Safety was assessed by number and severity of bleeding events. Statistical analyses included the Kruskal-Wallis test, Student’s T-test, and one-way ANOVA.

Results:

Of 121 patients identified, 74 met inclusion criteria. Participants were classified as nonobese (n = 33) or obese (n = 41). Initial LMWH anti-factor Xa levels differed significantly between groups (P = 0.045). The mean BMI of patients with a subtherapeutic initial level (29.02 kg/m²) differed significantly from those with a supratherapeutic initial level (35.8 kg/m²) (P = 0.030). No significant difference was found in adjusted enoxaparin dose between participants with and without obesity, but a significant difference existed between subtherapeutic and supratherapeutic groups (P < 0.001). Each group had 1 clinically relevant nonmajor bleed. Limitations included single-center design and small sample size.

Conclusions and Relevance:

Pregnant patients with obesity receiving treatment enoxaparin are likely to achieve target LMWH anti-factor Xa levels without initial dose adjustments. Morbidly obese patients, however, may still risk supratherapeutic levels. Pregnant patients without obesity were prone to subtherapeutic LMWH anti-factor Xa levels necessitating enoxaparin dose adjustments. Routine LMWH anti-factor Xa monitoring may be beneficial for obstetric patients receiving therapeutic enoxaparin, regardless of BMI.