A pregnant client reports experiencing frequent urination at night.

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

Serum creatinine and urea are waste products of protein metabolism that are normally filtered by the kidneys and excreted in urine.

In pregnancy, the glomerular filtration rate (GFR) increases by about 50%, which means more creatinine and urea are cleared from the blood.Therefore, serum creatinine and urea levels decrease in pregnancy compared to nonpregnant women.

A. Increased serum creatinine and urea levels are wrong because they indicate impaired kidney function or dehydration, which are not normal in pregnancy.

C. Unchanged serum creatinine and urea levels are wrong because they do not reflect the increased GFR in pregnancy.

D. Increased glomerular filtration rate is correct but it is not a finding regarding serum creatinine and urea levels, which are the focus of the question.

Normal ranges for serum creatinine and urea vary depending on the laboratory and the units used, but based on a nonpregnant reference interval of 45-90 μmol/l (0.51-1.02 mg/dl) for creatinine and 2.5-6.4 mmol/l (7-18 mg/dl) for urea, a serum creatinine of >77 μmol/l (0.87 mg/dl) and a blood urea of >8.5 mmol/l (24 mg/dl) should be considered outside the normal range for pregnancy.

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.