Is renal hyperfiltration protective in chronic kidney disease-stage 1 pregnancies? A step forward unravelling the mystery of the effect of stage 1 chronic kidney disease on pregnancy outcomes

BackgroundThe correlation between advanced or proteinuric chronic kidney disease (CKD) and adverse pregnancy outcomes is intuitive, although how early CKD affects pregnancy remains unknown. Glomerular hyperfiltration is a physiological response to pregnancy, correlated with outcomes in hypertension or collagen diseases. The aim of the study was to correlate first trimester hyperfiltration with pregnancy outcomes in stage 1 CKD patients. MethodsA historical prospective study was conducted on the database of our Unit, gathering all pregnant CKD patients referred since 1 January 2000. From 383 pregnancies referred in 2000-2013, 75 patients were selected (stage 1 CKD, referred within the 14th gestational week, singleton deliveries, absence of diabetes, hypertension or nephrotic proteinuria at referral, body mass index [BMI]<30); 267 low-risk' pregnancies, followed in the same setting, served as controls. Glomerular filtration rate (GFR) was assessed by Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) and dichotomized at 120mL/min. The odds for Caesarean section, prematurity, need for Neonatal Intensive Care Unit (NICU) were assessed by univariate analysis and logistic regression. ResultsRisk for adverse pregnancy outcomes was not affected by hyperfiltration (univariate OR GFR 120mL/min: Caesarean section 1.30 (0.46-3.65); preterm delivery: 0.84 (0.25-2.80)). In contrast, even in these cases with normal kidney function, stage 1 CKD was associated with prematurity (17.3% vs 4.9% P=0.001), lower birth weight (3027586 versus 3268500 P<0.001) need for NICU (12% vs 1.1% P<0.001). In the multivariate analysis, the risks were significantly increased by proteinuria and maternal age but not by GFR. ConclusionsIn pregnant Stage 1 CKD patients, hyperfiltration was not associated with maternal-foetal outcomes, thus suggesting a need to focus attention on qualitative factors, eventually enhanced by age, as vascular stiffness, endothelial damage or oxidative stress.