Even women with mild, stage 1 chronic kidney disease (CKD) have increased risks of adverse pregnancy outcomes, a new Italian study confirms. The findings might improve prenatal counseling and monitoring practices of women with CKD during pregnancy.
“The findings indicate that any kidney disease—even the least severe, such as a kidney scar from a previous episode of kidney infection, with normal kidney function—has to be regarded as relevant in pregnancy, and all patients should undergo a particularly careful follow-up,” lead researcher Giorgina Barbara Piccoli, MD, of the University of Torino in Italy, said in a news release. “Conversely, we also found that a good outcome was possible in patients with advanced CKD, who are often discouraged to pursue pregnancy.”
For the study, the investigators compared pregnancy outcomes in 504 women with CKD and 836 women without CKD, hypertension, diabetes, obesity, cardiovascular disease, or any other severe disease that might affect pregnancy. The women were participants in 2 separate cohorts from the Torino-Cagliari Observational Study (TOCOS), which assessed pregnancy outcomes prospectively for periods between 2000 and 2013.
The risk of adverse pregnancy outcomes increased with CKD stage, according to results published online ahead of print in the Journal of the American Society of Nephrology. The combined risk of pre-term delivery, need for care in the neonatal intensive care unit, and small infant size for gestational age was 34% for women with stage 1 CKD compared with 90% for women with stages 4 to 5. Similarly, the risk of severe cases of the above was 21% in stage 1 patients compared with 80% in patients with stages 4 to 5.
Classic risk factors could not fully explain the excess risks associated with CKD. Women with stage 1 CKD who gave birth prematurely were 3.1 to 3.7 times more likely to have hypertension, proteinuria, or systemic disease (such as diabetic nephropathy, lupus, collagen diseases, vasculitides, or kidney transplant). However, women with stage 1 CKD without these extra conditions still had almost twice the risk of adverse pregnancy-related outcomes. Notably, the risk of intrauterine death was similar between CKD patients and controls.
“By definition, patients with stage 1 CKD have normal kidney function; therefore, the significant differences compared with the low-risk control population demonstrate that kidney function impairment is not the only element to be taken into consideration for risk assessment in CKD pregnancy,” the researchers stated.
They recommend a prediction model, similar to that developed for preeclampsia, to help identify patients at higher risk.
- Piccoli, GB, et al. Journal of the American Society of Nephrology, 2015; doi: 10.1681/ASN.2014050459.
- American Society of Nephrology news release, March 12, 2015.