One of the symptoms in early pregnancy may be the need to urinate more often. The hormone progesterone is responsible for this increased need to urinate (during both day and night). This is because it has a relaxing effect on the bladder muscles. The pelvic area is also supplied with more blood during pregnancy, which stimulates the kidneys to work harder: Therefore, they produce more urine. In addition, in early pregnancy the uterus is small, but it grows quickly. Therefore, it puts more pressure on the bladder.