Heparin Prophylaxis Dosing for Antepartum Hospitalizations (HEPDOSE)

This study is a randomized control trial to compare gestational age-based dosing with standard dosing of unfractionated heparin for thromboprophylaxis of hospitalized antepartum patients. The investigators aim to determine the effect of dosing on receipt of neuraxial anesthesia and pregnancy outcomes and evaluate the pharmacokinetics and pharmacodynamics of unfractionated heparin in pregnancy.

Venous thromboembolism is one of the leading causes of maternal morbidity and mortality, and antepartum hospitalizations place pregnant patients at an even higher risk of developing thromboembolism. As a result, there is an increased emphasis on administering pharmacologic thromboprophylaxis for antepartum patients with prolonged hospitalizations. Previously, standard dosing of unfractionated heparin was widely adopted for thromboprophylaxis in the pregnant population. However, due to a suspected altered metabolism of unfractionated heparin in pregnancy resulting in a decrease response, the American College of Obstetricians and Gynecologists (ACOG) currently recommends considering gestational age-based dosing for unfractionated heparin for thromboprophylaxis in pregnancy with standard dosing as an alternative option. The data supporting altered dosing is very limited. In addition, increased dosing of heparin may result in challenges in anesthetic management, potentially limiting the receipt of neuraxial anesthesia resulting in increased need for general anesthesia associated with both increased maternal and fetal risks. The potential effects of higher prophylactic unfractionated heparin dosing in pregnant patients need to be further explored before being widely adopted for inpatient antepartum thromboprophylaxis. The investigators propose this study to provide a direct comparison of gestational age-based unfractionated heparin dosing to standard dosing of unfractionated heparin for pharmacologic thromboprophylaxis of hospitalized antepartum patients.

Eligibility Criteria:
Inclusion Criteria:

* At least 18 years of age
* Speak English or Spanish
* Antepartum admission for at least 72 hours at Ronald Reagan UCLA Medical Center
* Provides informed consent for study participation

Exclusion Criteria:

* Active or threatened antenatal bleeding
* Disseminated intravascular coagulation
* Risk of imminent delivery (delivery within 12 hours)
* Thrombocytopenia (platelet count \< 100 x 109)
* Elevated baseline aPTT (\> 36.2 seconds)
* Concern for hemolysis, elevated liver enzymes, low platelet count (HELLP) syndrome
* Congenital bleeding disorders (hemophilias)
* Receiving therapeutic or prophylactic anticoagulation (unfractionated heparin, low molecular weight heparin, oral anticoagulants) for alternative indication (e.g., acquired or inherited thrombophilia, history of VTE)
* History of heparin-induced thrombocytopenia (HIT)
* SARS-CoV-2 positive
* Cognitive impairment, psychiatric instability, or language barriers that limit their ability to provide informed consent
* Presence of a condition or abnormality that in the opinion of the Investigator would compromise the safety of the patient or the quality of the data.