Pregnancy complicated by heparin associated thrombocytopenia: management by a prospectively in vitro selected heparinoid (Org 10172).

A pregnant woman treated with unfractionated heparin for pelvic vein thrombosis in the 26th week of her first pregnancy developed heparin-associated thrombocytopenia. Diagnosis was verified by the heparin induced platelet activation (HIPA) assay, which revealed cross reactivity to various LMW heparins, but not to the LMW heparinoid Org 10172. Upon intravenous (i.v.) anticoagulation with the heparinoid Org 10172 the platelet count returned to normal within 6 days and remained stable throughout the entire treatment period. After 3 weeks i.v. treatment with Org 10172, administration was changed to the subcutaneous route. At term a healthy boy was delivered spontaneously. No Org 10172 was detected in the cord blood, while therapeutic levels were measured in the maternal blood. The infant's platelet count was normal, but serum from the cord blood induced platelet activation in the presence of heparin, indicating the transplacental passage of heparin-dependent maternal antibodies.