Risk of stones high among reproductive-aged women with prior pregnancies
Prior pregnancies appear to carry an increased risk of developing nephrolithiasis in women of reproductive age, a study suggests.
Analysing the association between pregnancy and kidney stone formation using the National Health and Nutrition Examination Survey data obtained from 2007 to 2012, researchers found the weighted national prevalence of nephrolithiasis among women ≤50 years to be 6.4 percent (95 percent CI, 5.4 to 7.6). The prevalence significantly differed when evaluated according to previous pregnancy status, being higher in women who had been pregnant than in those who had never been pregnant (7.5 vs 3.2 percent; p=0.0004).
On univariable analysis, women who had been pregnant were 2.44 (1.50 to 3.98) times as likely as those who had never been to have kidney stones. This increased likelihood of nephrolithiasis persisted despite controlling for age, ethnicity, obesity, history of diabetes, gout, hormone use, water intake and high sodium diet (odds ratio, 2.13; 1.31 to 3.45).
There was a notable increase in the prevalence of nephrolithiasis as the number of pregnancies increased, from 5.2 percent in women without a previous pregnancy to 12.4 percent in those with ≥3 pregnancies (p=0.001).
The mechanism underlying the increased prevalence of nephrolithiasis in women with prior pregnancies is believed to involve the lithogenic urinary changes occurring during pregnancy. For instance, increases in glomerular filtration of calcium associated with the intestinal hyper-absorption of calcium by the placental production of vitamin D (hypercalciuria), as well as in inhibitory factors of urinary crystallization and stone formation, may potentially boost stone proclivity in working- and reproductive-aged women thereafter. [J Bras Nefrol 2014;doi:10.5935/0101-2800.20140055]
In light of a strong association between nephrolithiasis and prior pregnancies, further investigation and identification of modifiable risk factors among pregnant patients is warranted in order to reduce the burden of stone disease in this population.