Low urea in pregnant women is mainly related to the increase of glomerular filtration rate during pregnancy, the increase of body fluids to dilute urea, and the poor diet in early stages. Urea is a toxin like creatinine. Therefore, the excretion of urea will increase during pregnancy, and the urea in the blood will naturally be low. In addition, the amount of body fluids in the body of a pregnant woman increases during pregnancy, which has a diluting effect on any substance, for example, the dilution of hemoglobin can lead to mild anemia. In the same way, dilution of urea can lead to low urea concentration. In the early stages of pregnancy, many pregnant women experience nausea and vomiting due to early pregnancy reactions, and their protein intake is also reduced, and urea is a metabolite of protein, so this is one of the causes of low urea.