Pharmacokinetics of Low Molecular Weight and Unfractionated Heparin in Pregnancy

This study's specific objectives include:

• Evaluating pharmacokinetic (concentration-time) and pharmacodynamic (concentration- effect) parameters for dalteparin and UFH prior to pregnancy, during the 1st, 2nd and 3rd trimesters and postpartum, using revised dosing protocols based on previous study.
• Determining therapeutic response to the heparins, i.e. live birth rate and lack of maternal or fetal complications, in relation to drug exposure, based on AUC.
• Documenting maternal and fetal complications during pregnancy for dalteparin and UFH, using the revised dosing protocols.

Inclusion criteria

• Two or more consecutive, otherwise unexplained miscarriages under 10 weeks of gestation, or, an otherwise unexplained intrauterine fetal demise of at least 10 weeks of gestation, and,
• Persistently positive antiphospholipid antibodies, or, presence of Factor V Leiden, or, Prothrombin 20210A, or, antithrombin, protein S, or protein C deficiency, or, hyperhomocysteinemia associated with the methylenetetrahydrofolate reductase (MTHFR) polymorphism.

Exclusion criteria

• Inability or refusal to give written informed consent.
• Inability or refusal to self-administer heparin throughout pregnancy.
• Hemoglobin value below 9.5 g/dL
• Heparin use is contraindicated.
• Renal disease.
• Documented history of thrombosis.