Purpose <p>Haematuria and proteinuria may point to kidney diseases, but may also be found incidentally. Among schoolchildren, many studies suggest their prevalence to around 1%. In neonates, the frequency and persistence of haematuria and/or proteinuria in the general population have so far not been investigated systematically.</p> Methods <p>In the course of the prospective KUNO-Kids Health&#xa0;Study, urine samples were collected and analysed by dipstick in asymptomatic neonates on days three to five after birth. Those with positive findings underwent a maximum of two follow-ups until 16&#xa0;weeks of age and factors associated with haematuria and/or proteinuria were explored.</p> Results <p>Of 509 participants with a urine sample available, 27% (<i>n</i> = 139) exhibited positive results. Of these, 58% (<i>n</i> = 81) had isolated haematuria, 21% (<i>n</i> = 29) had isolated proteinuria, and 21% (<i>n</i> = 29) had both. Of all children with positive urine tests, 76% (<i>n</i> = 105) underwent a first follow-up (mean 7&#xa0;weeks later), and only in 1.9% (<i>n</i> = 2) was a positive result found. In the second follow-up (mean 2&#xa0;weeks later), no positive results were detected anymore. Positive urine test results were more common in females and after vaginal delivery (<i>p</i> &lt; 0.001 and <i>p</i> = 0.037, respectively).</p> <p><i>Conclusion</i>: The present study identified haematuria and/or proteinuria in a significant proportion of healthy newborns shortly after birth, but results returned to normal within weeks in all participants available for follow- up. Thus, isolated findings of haematuria and/or proteinuria in newborns should be interpreted with caution.<Table Float="No" ID="Taba"> <tgroup cols="2"> <colspec align="left" colname="c1" colnum="1" /> <colspec align="left" colname="c2" colnum="2" /> <tbody> <row> <entry nameend="c2" namest="c1"> <p><b>What is known:</b></p> <p><i>• Previous studies have reported the prevalence and persistence of haematuria and/or proteinuria in school- age children, but data on haematuria and/or proteinuria in neonates are scarce.</i></p> </entry> </row> <row> <entry nameend="c2" namest="c1"> <p><b>What is new:</b></p> <p><i>• Positive urinary test results for haematuria and/or proteinuria are common after birth and were found in 27%.</i></p> <p><i>• Positive urinary test results returned to normal within 16&#xa0;weeks in all children tested.</i></p> </entry> </row> </tbody> </tgroup> </Table></p>