What causes oligohydramnios in late pregnancy?

The third trimester of pregnancy shows oligohydramnios, mainly considering whether to show fetal abnormalities, congenital urinary system abnormalities most common. For example, congenital kidney deficiency, such as the presence of urinary tract obstruction, this time the fetal urine production and excretion of obstacles, will show oligohydramnios. In addition, chromosomal abnormalities, can also cause oligohydramnios; placenta dysfunction. More common is expired pregnancy, or pregnancy hypertension disease, will cause placenta dysfunction. Insufficient placental perfusion, resulting in decreased urine production, will show oligohydramnios; in addition, there are fetal membrane lesions, or the mother shows hypovolemia, will show oligohydramnios.