Study: Pregnancy Increases Risk for Women to Develop First-Time Symptomatic Kidney Stones

An observational study reviewing the medical records for nearly 3000 female patients from 1984 to 2012 found that pregnancy increases the risk of a first-time symptomatic kidney stone, according to researchers at the Mayo Clinic.

The risk peaks close to delivery and then improves by 1 year after delivery, though a modest risk of developing kidney stones continues beyond 1 year after delivery, according to the study.

The study included 945 women who experienced a first-time symptomatic kidney stone and 1890 age-matched female control subjects. The researchers sought to determine whether the risk of a first-time symptomatic kidney stone increased with pregnancy and whether the risk varied across different time periods before, during, and after pregnancy.

"We suspected the risk of a kidney stone event would be high during pregnancy, but we were surprised that the risk remained high for up to a year after delivery," said Andrew Rule, MD, a Mayo Clinic nephrologist and the study's senior author, in a press release. "There also remains a slightly increased risk of a kidney stone event beyond a year after delivery. This finding implies that while most kidney stones that form during pregnancy are detected early by painful passage, some may remain stable in the kidney undetected for a longer period before dislodging and resulting in a painful passage."

According to the study authors, a symptomatic kidney stone event is the most common nonobstetric hospital admission diagnosis for pregnant women, and a symptomatic kidney stone event occurs in 1 of every 250 to 1500 pregnancies, most often occurring during the second and third trimesters. Though uncommon, kidney stones can cause significant complications, including preeclampsia, urinary tract infection, preterm labor and delivery, and pregnancy loss.

Rule noted that diagnosis of kidney stones during pregnancy can be challenging, given limited diagnostic imaging options due to concern about radiation exposure, and treatment can be complicated by obstetric concerns.

During pregnancy, ureteral compression, ureteral relaxation due to elevated progesterone hormones, increased urine calcium excretion, and elevated urine pH during pregnancy can lead to calcium phosphate stone formation, according to the study.

An awareness of a higher risk of kidney stones during pregnancy and the postpartum period can help health care providers offer diagnostic and preventive strategies for women.

"Urinary obstruction due to kidney stones can cause pain that some patients describe as the worst pain they have ever experienced," said Charat Thongprayoon, MD, Mayo Clinic nephrologist and study author, in the press release. "During pregnancy, a kidney stone may contribute to serious complication, and the results of this study indicate that prenatal counseling regarding kidney stones may be warranted, especially for women with other risk factors for kidney stones, such as obesity."

Dietary recommendations for preventing kidney stone disease include high fluid intake and a low-salt diet, in addition to appropriate calcium intake during pregnancy of at least 1000 milligrams per day.

REFERENCE

Mayo study finds that pregnancy increases risk for women to develop first-time symptomatic kidney stones. Mayo Clinic. Published April 15, 2021. Accessed April 16, 2021. https://newsnetwork.mayoclinic.org/discussion/mayo-clinic-study-finds-that-pregnancy-increases-risk-for-women-to-develop-first-time-symptomatic-kidney-stones/