Increased unfractionated heparin requirements with decreasing body mass index in pregnancy

Prophylactic Unfractionated Heparin in Antepartum Hospitalizations: A Randomized Controlled Trial

OBJECTIVE

To assess the effect of gestational age-based dosing of unfractionated heparin (UFH) compared with standard dosing of UFH for thromboprophylaxis on an elevated serum activated partial thromboplastin time (aPTT) during prolonged antepartum hospitalizations.

METHODS

This was a randomized trial of pregnant persons who were admitted in the antepartum period for at least 72 hours. Participants were randomly allocated to the standard dose of UFH (5,000 units subcutaneously every 12 hours) or the gestational age-based dose of UFH (first trimester [less than 14 weeks]: 5,000 units subcutaneously every 12 hours; second trimester [14-27 6/7 weeks]: 7,500 units subcutaneously every 12 hours; third trimester (28 weeks or more): 10,000 units subcutaneously every 12 hours). The primary outcome was the proportion of antepartum patients who had an elevated serum aPTT value above the normal range (more than 36.2 seconds) 6 hours after an UFH dose. Secondary outcomes included the development of venous thromboembolism (VTE) and reported side effects of heparin administration.

RESULTS

Between December 15, 2020, and April 1, 2022, 97 patients with antepartum hospitalizations were screened and 46 were randomized: 22 allocated to standard dosing and 24 allocated to gestational age-based dosing of UFH. A significantly greater proportion of antepartum patients who received gestational age-based dosing had an abnormal elevation in aPTT compared with those who received standard dosing (33.3% vs 4.8%, P =.02). Gestational age-based dosing resulted in higher maximum [interquartile range] aPTT (30.4 [27.4, 37.5] vs 26.6 [23.0, 29.6], P =.01) and anti-Xa levels (0.09 [0.09, 0.11] vs 0.09 [0.09, 0.09], P =.04). There was no significant difference in VTE between groups ( P =.47).

CONCLUSION

Gestational age-based dosing of UFH for thromboprophylaxis of antepartum hospitalizations was associated with significantly increased rates of elevated coagulation parameters compared with standard fixed dosing. This study suggests a need for close monitoring if higher doses of UFH during pregnancy are used later in gestation. The efficacy of gestational age-based dosing compared with standard dosing for UFH to prevent thromboembolic events remains an area for future investigation.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov , NCT04635839.

Anticoagulant therapy for women: implications for menstruation, pregnancy, and lactation

Estrogen exposure, in the setting of pregnancy, the postpartum state, combined hormonal contraceptives (CHCs), or hormone therapy use, has been clearly associated with increased rates of venous thromboembolism (VTE). Although recurrence rates are low in these settings, up to 70% of anticoagulated menstruating individuals experience abnormal or heavy menstrual bleeding (HMB), which commonly results in iron deficiency with or without anemia. Patients taking rivaroxaban appear to experience higher rates of HMB compared with those on apixaban, dabigatran, or warfarin. HMB can often be diagnosed in a single visit with a good menstrual history assessing for factors with a known association with increased or heavy bleeding, such as changing pads or tampons more often than every 2 hours, clots larger than a quarter, and iron deficiency (ferritin <50  ng/mL). HMB can be managed with hormonal therapies, including those associated with VTE risk, such as CHCs and depot-medroxyprogesterone acetate (DMPA). In many cases, continuing CHCs or DMPA while a patient is therapeutically anticoagulated is reasonable, so long as the therapy is discontinued before anticoagulation is stopped. Modification of the anticoagulation regimen, such as decreasing to a prophylactic dose in the acute treatment period, is not currently recommended. For patients who are currently pregnant, low-molecular-weight heparin (LMWH) is still standard of care during pregnancy; routine monitoring of anti-factor Xa levels is not currently recommended. Warfarin or LMWH may be considered in the postpartum setting, but direct-acting oral anticoagulants are currently not recommended for lactating patients.

Management of Venous Thromboembolism in Pregnancy

PURPOSE OF REVIEW

This manuscript addresses the risks for venous thromboembolism (VTE) during pregnancy and the associated challenges of both diagnosis and treatment.

RECENT FINDINGS

The obstacles to diagnosis given lack of specificity of typical biomarkers to predict VTE in pregnancy, as well as the unique fetal and bleeding risks introduced by managing massive pulmonary embolism (PE) with thrombolytics or thrombectomy are highlighted. VTE during pregnancy and the postpartum window occurs at a 6-10-fold higher rate compared with age-matched peers and is a major cause of morbidity and mortality. Hypercoagulability persists for 6-8 weeks after delivery with the highest risk of PE being postpartum. The lack of randomized trials in pregnant women leads to variability in practice, which are largely based on expert consensus or extrapolation from non-pregnant cohorts. The standard treatment of VTE in pregnancy is anticoagulation with low molecular weight heparin (LMWH), which like unfractionated heparin does not cross the placenta and is not teratogenic. LMWH is preferred given the negligible risk for heparin-induced thrombocytopenia and osteoporosis, better bioavailability, and a predictive dose response. Depending on the severity of the VTE, additional treatments including thrombolysis, thrombectomy, inferior vena cava filter placement, or venous stenting may be used. Management requires balancing the competing bleeding and thrombotic risks during labor and delivery and factoring the impact of treatment on the fetus. A multidisciplinary team involving hematology, obstetrics, anesthesia, vascular medicine, and cardiology is critical for safe and timely management. The design and execution of prospective, randomized trials to specifically address optimal diagnosis and management are a top priority in obstetric hematology.