Pregnancy changes a lot on the surface and in the body. Most pregnant women develop hydronephrosis, commonly in the middle and late stages of pregnancy. In most of them, hydronephrosis is not harmful to the body and is called physiologic hydronephrosis. This type of hydronephrosis is related to the altered hormone levels in the body after pregnancy and the pressure of the enlarged fetus on the urinary tract. In a small number of people, hydrocele may also result from blockage of the urinary tract by urinary stones, tumors or blood clots, and compression by lesions outside the urinary tract. Pregnant women with physiological hydronephrosis mostly have no discomfort, so observation is often used. Since hydronephrosis mostly occurs on the right side, you can try lying on the left side to relieve the pressure of the enlarged uterus on the ureter to relieve hydronephrosis. A small number of people may have back pain or fever due to secondary infection of hydronephrosis. Severe pain may stimulate uterine contractions leading to preterm labor and miscarriage, therefore, it needs to be actively managed. Co-infection and severe hydronephrosis also need to be treated aggressively. The first treatment is conservative, with medication to relieve pain and control urinary tract infection. If conservative treatment does not work, temporary placement of a stent tube or nephrostomy may be considered to drain the hydronephrosis, control the infection, protect the kidney function, and further evaluate the treatment after delivery.