BACKGROUND: Pregnancy induced hypertension (PIH) is a common cause of maternal morbidity and death in late pregnancy. Pulmonary edema, although infrequently encountered, may cause death in severe cases of PIH. However, the mechanisms that account for pulmonary edema have not been clarified. Mobilization of peripheral edema, excess fluid intake, myocardial dysfunction, and reduced plasma protein concentration are factors that have been postulated as contributing to the development of pulmonary edema in this syndrome. Colloid osmotic pressure is a principal regulator of capillary fluid exchange. METHODS: In a study of 50 normotensive and severe PIH patients who underwent cesarean section, peripartum plasma colloid osmotic pressure, serum albumin, and total serum protein were compared. RESULTS: Both groups exhibited significantly lower plasma colloid osmotic pressure in the postpartum period than that measured antepartum (p<0.05). The mean antepartum plasma colloid osmotic pressure in severe PIH patients was significantly lower than in normotensive subjects (p<0.05). CONCLUSIONS: We believe that serial COP measurments may be helpful to guide optimal fluid management in severe PIH patients.