What causes pregnancy hydronephrosis?

There are many reasons for pregnancy hydronephrosis, one of the most important is because of the physiological changes unique to women's body so that the incidence of hydronephrosis significantly increased. For example, during pregnancy, the secretion of progesterone and estrogen in women's body will increase, causing the smooth muscle of the fallopian tubes to relax, slowing down the motility

of the fallopian tubes.