A 35-year-old Japanese nulliparous woman exhibited rapid weight gain (6 kg/7 days), reduced antithrombin activity and platelet count at 37 weeks of gestation without hypertension or proteinuria, and underwent cesarean section. Postnatally, pulmonary edema developed for 7 days, with transient hypertension and proteinuria, and bodyweight loss (14.6 kg) by 14 days postpartum. Platelet count and antithrombin activity normalized promptly postpartum. Despite a life-threatening clinical condition due to enhanced vascular permeability, neither hypertension nor proteinuria appeared antenatally. Determining antithrombin activity and platelet count may be useful for distinguishing between women with pathological edema and physiological edema.