A pregnant client reports experiencing frequent urination at night.

The nurse explains that this symptom is primarily caused by:.

This is because a pregnant client may experience frequent urination at night due to increased urinary output caused by the increased blood volume and renal function during pregnancy.

This symptom is more common in the first and third trimesters.

Choice A is wrong because increased glomerular permeability does not cause nocturia, but it may cause proteinuria, which is the presence of protein in the urine.

Choice B is wrong because decreased renal blood flow does not cause nocturia, but it may cause renal ischemia, which is a condition where the kidneys do not receive enough blood supply.

Choice C is wrong because increased tubular reabsorption does not cause nocturia, but it may cause water retention and edema, which are swelling of the body tissues due to fluid accumulation.

Back pain is a common symptom experienced due to increased muscle strain during pregnancy.

As the uterus grows and the center of gravity shifts, there is more pressure on the lower back muscles and ligaments.

This can cause pain, difficulty with balance, and reduced activity.

Choice A is wrong because leg cramps are not caused by muscle strain, but by other factors such as dehydration, electrolyte imbalance, or compression of blood vessels.

Choice C is wrong because pelvic pain is not a typical symptom of musculoskeletal changes during pregnancy.

Pelvic pain can be caused by other conditions such as urinary tract infection, preterm labor, or pelvic girdle pain.

Choice D is wrong because carpal tunnel syndrome is not a result of muscle strain, but of fluid retention and swelling that compresses the median nerve in the wrist.

This can cause numbness, tingling, or pain in the hand and fingers.