Background: Prognostic criteria to inform women with moderate to severe renal insufficiency who wish to bear children are not well established.
Study design: Longitudinal multicenter cohort study.
Settings & participants: Nondiabetic white women with pregnancies proceeded beyond the 20th week and estimated glomerular filtration rate (GFR) less than 60 mL/min/1.73 m(2) (<1 mL/s/1.73 m(2)) before conception.
Predictors: Baseline GFR and proteinuria (exposure); other clinical characteristics at conception (covariates).
Outcomes & measurements: Difference in GFR decreases before conception versus after delivery (mixed linear models); low birth weight (<2,500 g), and maternal renal survival (logistic and Cox regressions).
Results: 49 women were studied. Mean serum creatinine and GFR at conception were 2.1 +/- 1 (SD) mg/dL (186 +/- 88 micromol/L) and 35 +/- 12 mL/min/1.73 m(2) (0.58 +/- 0.2 mL/s/1.73 m(2)), respectively. Overall mean GFR after delivery was less than before conception (30 +/- 13.8 versus 35 +/- 12.2 mL/min/1.73 m(2) [0.50 +/- 0.23 versus 0.58 +/- 0.20 mL/s/1.73 m(2)]; P < 0.001), but the rate of GFR decrease did not change (0.55 +/- 0.8 versus 0.50 +/- 0.3 mL/min/mo [0.0092 +/- 0.013 versus 0.0083 +/- 0.005 mL/s/mo]; P = 0.661). Independent of potential confounders, the combined presence of baseline GFR less than 40 mL/min/m(2) (<0.67 mL/s/m(2)) and proteinuria with protein greater than 1 g/d, but not either factor alone, predicted faster GFR loss after delivery compared with before conception (1.17 +/- 1.23 versus 0.55 +/- 0.39 mL/min/mo; difference, 0.62 mL/min/mo; 95% confidence interval [CI], 0.27 to 0.96 mL/min/mo [0.020 +/- 0.021 versus 0.0092 +/- 0.007 mL/s/mo; difference, 0.10 mL/s/mo; 95% CI, 0.005 to 0.016 mL/s/mo]). The presence of both risk factors, but not either alone, also predicted shorter time to dialysis therapy or GFR halving (N = 20; hazard ratio, 5.2; 95% CI, 1.7 to 15.9) and low birth weight (N = 29; odds ratio, 5.1; 95% CI, 1.03 to 25.6).
Limitations: Generalizability to other settings; study power.
Conclusion: In women with renal insufficiency, the presence of both GFR less than 40 mL/min/1.73 m(2) (<0.67 mL/s/m(2)) and proteinuria with protein greater than 1 g/d before conception predicts poor maternal and fetal outcomes.