Pregnancy increases the risk of developing symptomatic kidney stones for the first time, which reaches its maximum until the time of delivery, but may persist even a year later, according to a population-based, case-controlled study.
“We suspected that the risk of a kidney stone event would be high during pregnancy, but we were surprised that the risk remained high until one year after delivery,” said author Andrew Rule, MD, nephrologist of the Mayo Clinic in Rochester, Minnesota. , said in a statement from his institution.
“[So] while most kidney stones that form during pregnancy are soon detected by a painful passage, some may remain stable in the kidney without being detected for a longer period before being evacuated and [again] resulting in a painful passage, “he added.
The study was published online April 15 a The American Journal of Kidney Diseases by Charat Thongprayoon, MD, also of the Mayo Clinic, and colleagues.
“The results of this study indicate that prenatal counseling on kidney stones may be justified, especially for women with other risk factors for kidney stones, such as obesity“, he pointed out.
Stone trainers for the first time
The observational study included 945 first-time symptomatic trainers of kidney stones between 15 and 45 years of age who were compared with female controls coinciding with the 1890 Rochester Epidemiology Project. The latter is a medical records linking system for almost all medical care administered in Olmsted County, Minnesota.
Compared with nonpregnant women, the probabilities of symptomatic kidney stone forming in a pregnant woman were similar in the first trimester (odds ratio, 0.92; Pg =, 8), began to increase during the second quarter (OR, 2.00; Pg = .007), further increased during the third quarter (OR, 2.69; Pg = 0.001), and peaked between 0 and 3 months postpartum (OR, 3.53; Pg<.001). The risk returned to baseline a year after delivery.
These associations persisted after adjustment for age and race or for diabetes, hypertensionand obesity. These results did not differ significantly by age, race, time period, or number of previous pregnancies.
The risk of a pregnant woman developing symptomatic kidney stones was higher in obese women compared to those of normal weight (Pg= .01).
And compared with women who had not been pregnant before, a previous pregnancy also increased the risk of suffering a symptomatic kidney stone by about 30% (OR, 1.29; Pg= 0.03), although two or more previous pregnancies did not significantly increase the symptomatic risk of kidney stone.
Therefore, “it can be inferred that the probabilities of a kidney stone symptom occurring at maximum at the time of delivery,” the authors emphasize.
“The odds of a symptomatic kidney stone for the first time decreased over time and were completely attenuated and were no longer statistically significant at 12 months postpartum,” the authors add.
Thongprayoon says there are several physiological reasons why pregnancy can contribute to the formation of kidney stones.
During pregnancy, ureteral compression and ureteral relaxation due to high progesterone levels can cause urinary stasis.
In addition, increased urinary calcium excretion and high pH of urine during pregnancy may favor the formation of calcium phosphate stones. It should be noted that almost all early pregnant stone builders had calcium phosphate stones.
“During pregnancy, a kidney stone can contribute to serious complications,” Thongprayoon explained.
General dietary recommendations for preventing kidney stones include drinking plenty of fluids and consuming a low-salt diet.
The study was supported by the Mayo Clinic O’Brien Urology Research Center and a grant from the National Institute of Diabetes and Digestive and Renal Diseases. The authors have not disclosed any relevant financial relationship.
I am Renal Disorder.Published online April 15, 2021. Summary