Objective: Nephrolithiasis occurring during pregnancy may be associated with an elevated risk of preterm delivery and other adverse birth outcomes. The goal of this study was to describe the association between these outcomes and admission for nephrolithiasis during pregnancy.
Methods: We performed a retrospective cohort study using birth certificate records linked to Washington State hospital discharge data from 1987-2003 to compare pregnant women admitted for nephrolithiasis and randomly selected pregnant women without nephrolithiasis. The main outcomes of interest were preterm delivery, premature rupture of membranes at term or before 37 weeks of gestation, low birth weight, and infant death.
Results: A total of 2,239 women were admitted for nephrolithiasis, yielding a cumulative incidence of 1.7 admissions per 1,000 deliveries. Women admitted for nephrolithiasis during pregnancy had nearly double the risk of preterm delivery compared with women without stones (adjusted odds ratio 1.8, 95% confidence interval 1.5-2.1). However, they were not at higher risk for the other outcomes investigated. A total of 471 (25.9%) women had one or more procedures for kidney stones during prenatal hospitalization. Undergoing a procedure and the trimester of admission did not affect the risk of preterm delivery.
Conclusion: Although the incidence of nephrolithiasis requiring hospital admission during pregnancy is relatively low, these women have an increased risk of preterm delivery. This has potential implications for counseling of pregnant women with kidney stones requiring hospital admission. Additionally, it may prompt definitive treatment of small, asymptomatic stones in women during reproductive years.