# Frequency and short-term persistence of haematuria and/or proteinuria in neonates: a cohort study

## TL;DR

This study finds that about a quarter of newborns show signs of blood or protein in urine, but these usually disappear within weeks.

## Contribution

The study is the first to systematically investigate the frequency and short-term persistence of haematuria and proteinuria in neonates.

## Key findings

- 27% of asymptomatic neonates showed haematuria and/or proteinuria in initial urine tests.
- Positive results returned to normal within 16 weeks in all followed-up children.
- Positive findings were more common in females and after vaginal delivery.

## Abstract

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.

In the course of the prospective KUNO-Kids Health 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 weeks of age and factors associated with haematuria and/or proteinuria were explored.

Of 509 participants with a urine sample available, 27% (n = 139) exhibited positive results. Of these, 58% (n = 81) had isolated haematuria, 21% (n = 29) had isolated proteinuria, and 21% (n = 29) had both. Of all children with positive urine tests, 76% (n = 105) underwent a first follow-up (mean 7 weeks later), and only in 1.9% (n = 2) was a positive result found. In the second follow-up (mean 2 weeks later), no positive results were detected anymore. Positive urine test results were more common in females and after vaginal delivery (p < 0.001 and p = 0.037, respectively).

Conclusion: 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.
What is known:• 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.What is new:• Positive urinary test results for haematuria and/or proteinuria are common after birth and were found in 27%.• Positive urinary test results returned to normal within 16 weeks in all children tested.

What is known:

• 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.

What is new:

• Positive urinary test results for haematuria and/or proteinuria are common after birth and were found in 27%.

• Positive urinary test results returned to normal within 16 weeks in all children tested.

The online version contains supplementary material available at 10.1007/s00431-026-06859-w.