If the urine of a pregnant woman is high in red blood cells, the possible causes are: 1. When combined with urinary tract infection, there can be congestion and edema of the mucous membrane epithelium of the urinary tract. This can be accompanied by a small number of red blood cells in the urine, and further urine culture tests are needed. The patient may have symptoms of urinary tract irritation, but may not have symptoms of urinary frequency and urgency. 2. If the pregnant woman has urinary stones, she may have high erythrocytes and may have a history of significant back or abdominal pain, which requires an ultrasound examination of the urinary system for further screening. 3. But at this time, the patient may not have any conscious symptoms, only high red blood cells are found during urine tests. In this case, it is recommended to drink more water and urinate more often, and to perform ultrasound examination of the urinary system and regular monitoring of urine routine to understand the changes of red blood cells.