Idiopathic chylous ASCITES in pregnancy is extremely rare. Here, we report a 24-yr-old patient with idiopathic chylous ASCITES in pregnancy. The patient was hospitalized in Xiamen Maternity and Child Health Care Hospital, Xiamen China in 2014 due to G1P0 intrauterine pregnancy 39+2 week, LOA, and time of labor. The patient gave birth to a live baby boy (3. 6 kg) by spontaneous vaginal delivery, with complete delivery of placenta. Three hours after delivery, the patient reported abdominal distension and pain, as well as asthma. Later, milky white liquid was drawn from left lower abdomen by puncture. Exploratory laparotomy was performed, and 800 ml milky white liquid was drawn from the abdominal cavity. Subsequently, drainage tube was placed in the ab-dominal cavity, and the abdomen was closed. After the surgery, the patient was given low-fat diet, supplemented with parenteral nutrition support and intravenous injection of antibiotics. Extubation was performed on day 3. On day 7 after surgery, the mother and baby left the hospital without any health problems. No abnormality was observed during six months of follow-ups. Idiopathic chylous ASCITES in pregnancy may be related to congenital lymphatic system dysplasia, and directly caused by chylous flow from ducts into abdominal cavity induced by progesterone during pregnancy or pressure from enlarged uterus during late pregnancy. After pregnancy, the disease is cured by the release of disease cause and the reduction of thoracic duct pressure.