The diagnosis of preeclampsia superimposed on underlying kidney disease is complicated by physiological changes in renal function, blood pressure and proteinuria during pregnancy. Previous studies have demonstrated a significant increase in proteinuria during pregnancy in women with diabetic nephropathy in the absence of superimposed preeclampsia. There is a paucity of studies addressing changes in proteinuria during pregnancy in other conditions causing chronic kidney disease. A retrospective audit of changes in urine protein:creatinine ratios in 68 pregnancies to women with preconception proteinuria was performed, to determine whether changes in proteinuria may be useful in diagnosing preeclampsia. A 100% or greater increase in proteinuria from baseline increase was regarded as a significant change. In 51 pregnancies (75%) the peak urine protein:creatinine ratio did not rise significantly from values at the start of pregnancy. Where a greater than doubling of urine protein:creatinine ratio was seen, 12 of 17 pregnancies (70%) were judged clinically to have superimposed preeclampsia A significant increase in proteinuria also occurred in 3 women with lupus nephritis, and 2 with diabetic nephropathy, in the absence of preeclampsia. Larger studies of women with chronic kidney disease would be important to determine whether changes in proteinuria during pregnancy may be of diagnostic value for superimposed preeclampsia.
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