In pregnancy, nephrolithiasis often occurs in the second and third trimesters due to progesterone-induced ureteral dilation and decreased peristalsis, which lead to urinary stasis. In addition, pregnancy is associated with increased urinary calcium excretion. These combined effects predispose pregnant women to stone formation.
Some patients with renal stones also experience irregular contractions due to the proximity of the uterus to the inflamed ureter because the uterus is sensitive and reactive to prostaglandins released from ongoing inflammation
Diagnostic imaging of choice for evaluating abdominal pain in pregnancy, especially if renal stones are suspected, is renal and pelvic ultrasonography, rather than CT scan, to avoid unnecessary radiation to the fetus.