Pregnancy is associated with extensive haemostatic changes. As n-3 fatty acids have been shown to interfere with the haemovascular balance, we have studied whether dietary supplementation with n-3 fatty acids in late pregnancy interferes with blood lipids, serum urate and key-variables within coagulation and fibrinolysis. 84 women in the 30th week of pregnancy were randomly assigned to fish oil or either olive oil or no oil supplementation as controls (2:1:1). Blood samples were collected at baseline and at the 37th week of pregnancy. In serum, lipids and urate were determined. In plasma, coagulation and fibrinolysis variables were quantified. At the 37th week, a significantly higher level of fibrin degradation products (p<0.01) were seen in the fish oil group. A higher mass-length ratio of the fibrin fibres in the fish oil group might help to explain this observed higher concentration of fibrin degradation products, since no other significant differences within the coagulation and fibrinolysis systems were seen. No effects of fish oil on blood lipids and serum urate were seen.