Pregnancy is associated with an elevated risk for a first-time symptomatic kidney stone, according to the findings of a case-control study. The risk begins to increase in the second trimester and peaks just after delivery.
Compared with nonpregnant women, women in the second and third trimester of pregnancy have significant 2.0- and 2.7-fold increased odds of forming asymptomatic kidney stones, a team led by Andrew D. Rule, MD, of Mayo Clinic in Rochester, Minnesota, reported in the American Journal of Kidney Diseases. From 0 to 3 months after delivery, women had a 3.5-fold increased risk of kidney stone formation. Kidney stone risk returned to baseline by 1 year after delivery. The study found no significant difference in kidney stone risk between nonpregnant women and those in their first trimester of pregnancy.
The authors concluded that prenatal counseling of kidney stone risk with pregnancy may be warranted, particularly for women with other risks for kidney stones, such as obesity, diabetes, or a family history of kidney stones.
The study included 945 women aged 15 to 45 years who had a first-time symptomatic kidney stone and an age-matched control group of 1890 women.
As a result of the study’s case-control design, the investigators noted that the rate of stone events in pregnancy could not be determined from their data.
Kidney stone formation could be due to physiologic changes associated with pregnancy, according to the investigators. They noted, for example, that an enlarging uterus compresses ureters against fixed iliac vessels, and elevated progesterone levels impair ureteral peristalsis. Both of these factors contribute to the hydronephrosis observed in up to 90% of pregnancies, the authors stated. “Urinary stasis from hydronephrosis prolongs the contact time between lithogenic metabolites (eg, calcium) in the urine, enhancing crystallization and stone formation,” they explained.