It may be normal for the amount of urine to become less in mid-pregnancy, but a 24-hour urine output of less than 400 ml is not normal, and may be caused by hypertension and renal hypoplasia during pregnancy. 1. Normal situation: women usually water intake is too small, the body metabolism after the formation of the amount of urine is also relatively small, mid-pregnancy has a small amount of urine performance is normal. If the mid-pregnancy weather is hotter or the environment temperature is high, the body will discharge more sweat, urine concentration, there will be a decrease in the amount of urine phenomenon, is also a normal performance. 2. Hypertension in pregnancy: women with gestational hypertension, mid-pregnancy blood pressure is relatively high and unsatisfactory control, proteinuria, edema, may cause damage to the kidneys, there is a decrease in the amount of urine, this is not normal. 3. Renal decompensation: patients with kidney disease, if it progresses to the stage of renal failure, the kidneys lose their filtration function, and the urine output will gradually decrease, which is also abnormal. Whether it is normal to have less urine in mid-pregnancy, you have to go to the hospital to judge through examination.