Low urea nitrogen may be caused by physiological factors of pregnant women such as increase in glomerular filtration rate and increase in blood volume, which usually has no effect on pregnant women, but it may also be caused by too little protein intake, which has some effect. 1. Increase in glomerular filtration rate: During pregnancy, the kidneys of pregnant women will increase their load, and the glomerular filtration rate will increase, which will lead to a decrease in the concentration of urea nitrogen in the blood, which is a normal physiological phenomenon, and it has no effect on pregnant women. 2. Increased blood volume: During pregnancy, pregnant women’s blood volume increases, water and sodium retention, body fluids will be diluted to a certain extent, resulting in low urea nitrogen concentration, generally has no effect, but may lead to edema, lower blood pressure. 3. Protein intake is too low: during pregnancy, due to fetal growth and development, protein consumption increases, if there is vomiting or protein intake is not enough, there may be a low urea nitrogen concentration, which may result in fetal growth restriction, have a certain impact. If the urea nitrogen is low, the diet should be supplemented with some protein-rich foods, and more vegetables and fruits can be eaten to supplement vitamins. If the urea nitrogen is too low, you should consult your doctor and take treatment under the doctor’s advice.