Aims: In patients with immunoglobulin A (IgA) nephropathy, postnatal renal outcomes vary depending on kidney function and proteinuria. However, whether a decrease in proteinuria prior to conception improves postnatal maternal renal outcomes is unknown. Methods: This was a single-center retrospective study. A total of 52 pregnant women with biopsy-proven IgA nephropathy was enrolled in the study between January 2004 and December 2009. We collected data on proteinuria, which had been measured 1 year prior to conception, at conception, during pregnancy, and postnatally. The study outcomes included changes in estimated glomerular filtration rate (eGFR) and proteinuria. Results: The median serum creatinine, eGFR, and proteinuria levels at conception were 0.8 (0.5 - 2.6) mg/dl, 91.2 (24.1 - 157.0) ml/min, 0.7 (0.0 - 3.5) g/g, respectively. Compared with values measured at conception, serum creatinine (0.8 - 1.0 mg/dl, p < 0.01) and proteinuria (0.7 - 1.5 g/g, p < 0.01) increased significantly postnatally, while eGFR decreased (91.2 - 77.8 ml/min, p < 0.01). In a multiple linear regression analysis, proteinuria at conception were independently associated with a faster decline in postnatal maternal eGFR (β = 4.50, p < 0.05). In addition, a less decline in maternal eGFR was observed in patients with a reduction in proteinuria (> 30%) prior to pregnancy, compared with those with a less reduction (≤ 30%). As for newborn outcomes, preterm delivery, caesarean section, low birth weight < 2,500 g, and need for neonatal intensive care were 15.4%, 46.2%, 25.0% and 7.7%, respectively. Conclusions: This study showed that in women with IgA nephropathy, proteinuria was significantly associated with the deterioration of postnatal maternal renal outcomes. Our study also suggests that a strategy for reducing proteinuria prior to pregnancy is required to preserve kidney function after delivery.
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