Another limitation is the possibility of uncontrolled confounding. Previous validation studies on diabetes mellitus and rheumatic disease have suggested that these diagnoses are well captured and are unlikely to be important confounders in our study.20,21 Urinary dipstick and blood-pressure measurements are routinely performed at all pregnancy visits, and essential hypertension and kidney disease are recorded, although these reports have not been validated. We cannot rule out the possibility that mild kidney disease may have remained undetected or unreported during pregnancy in some women. Nevertheless, even if this were the case, preeclampsia would still be an important clinical marker for an increased risk of renal disease in these women