We describe a case where danaparoid was used prophylactically in a high-risk twin pregnancy following the development of heparin-allergy while on prophylactic dalteparin. Danaparoid was substituted for dalteparin at 20 weeks of pregnancy following the development of a severe skin reaction while on the low molecular weight heparin. Although there was no significant fall in platelet count, an aggregation assay for heparin-induced thrombocytopaenia was positive. The skin lesions rapidly resolved following the change to subcutaneous danaparoid. Delivery was by emergency caesarian section at 35 weeks under a general anaesthetic, as a dose of danaparoid had been given 6 h prior to delivery. A sample of breast milk showed no anti-activated factor X activity. Danaparoid was continued post-delivery until the patient was fully warfarinized. To our knowledge, there are no previous reports of the use of danaparoid in this setting.