Serum lipids increase during pregnancy. However, data are scarce for lipid changes in pregnant women with heterozygous familiar hypercholesterolemia (FH). The purpose of the present study was to examine plasma lipids and lipoproteins during pregnancy in women with FH. In 22 pregnant women blood samples were collected at gestational weeks 17-20 (baseline), 24, 30 and 36. Total- and LDL cholesterol increased significantly between baseline and gestational week 36 by 29% and 30%, respectively, compared to 25% and 34% in a reference group of 149 healthy pregnant women. Notably, the plasma lipid concentrations in the FH women were much higher than in the reference women. Triglycerides increased (P<0.05) by 116% and 103%, in the FH group and reference group, respectively. HDL cholesterol was unchanged in both groups. Moreover, apolipoprotein B increased significantly during pregnancy in the FH women, whereas apolipoprotein A1 and lipoprotein (a) were unchanged. Pregnancy outcomes in the FH group did not differ significantly from those in the reference group. In conclusion, the relative increase in plasma lipids was similar in pregnant women with FH and in healthy women, but the absolute magnitude was considerably larger in pregnant FH women.