How the bladder works
Could it be an infection?
What women find helpful for frequent urination or bladder infections
Passing urine frequently is nothing new to a pregnant woman. It can even be one of the first early signs that let her know she is pregnant and one of the main reasons she will have broken sleep during late pregnancy.
Up to about 14 weeks of the pregnancy passing more urine is mainly because of an increase in urine production by the kidneys, due to pregnancy hormonal changes. To a lesser degree frequent urination can result from pressure on the bladder from the growing uterus as well as an increased blood supply to the pelvis.
By the middle of the pregnancy (from about 14 to 30 weeks), frequent urination tends to improve somewhat as the kidneys produce less urine and the uterus moves up and out of the pelvis, away from the bladder.
During late pregnancy (from about 30 weeks onwards) the increased weight of the growing baby and uterus start to put more pressure on the bladder. This may worsen or improve once the baby's head engages.
Frequent urination may be made worse if your pelvic floor muscle is weakened. This can be due to the affects of the hormone progesterone during pregnancy, and possibly not doing enough pelvic floor exercises. This is also why frequent urination can persist after the birth. You may wish to read pelvic floor exercises.