During pregnancy, what renal changes occur?

• A. Kidneys shrink slightly
• B. No changes in kidney size
• C. Kidneys increase in length and ureters get longer
• D. Ureters shorten

Answer: (C)

During pregnancy, hormonal and mechanical factors push urinary-tract changes. Progesterone relaxes smooth muscle, and the growing uterus mechanically compresses and displaces the ureters. This leads to dilation of the renal pelvis and ureters (hydronephrosis/hydroureter), and the kidneys can become slightly enlarged as blood flow and GFR increase to meet the metabolic needs of pregnancy. So the combination is that the kidneys may lengthen a bit and the ureters become longer, which is why this option best describes the renal changes during pregnancy.