A new research has revealed that expectant mothers should not smoke during pregnancy as it might impair children's kidney.

It is said that children who are born to women who smoked during their pregnancy were more likely to show signs of kidney damage by the age of three, compared to those born to non-smoking mothers.

The findings showed that maternal smoking during pregnancy was one of the risk factors of childhood proteinuria, abnormal amount of protein in urine -- a sign of kidney disease.

The effects on kidney health were evident in 3-year-old children.

Koji Kawakami from Kyoto University, in Japan, "Maternal smoking during pregnancy is known to be associated with preterm birth, low birth weight, and neonatal asphyxia. The findings from this study suggest an additional adverse effects of maternal smoking during pregnancy".

For the study, the team looked for the presence of proteinuria in urinary tests from 44,595 children from pregnancy to three-years of age.

The results showed that the prevalence rates of proteinuria in children at age three in the maternal smoking groups -- none, past, and current -- were 78.9 per cent, 4.4 per cent and 16.7 per cent, respectively.

Maternal smoking during pregnancy was associated with a 1.24-times increased risk of child proteinuria compared with no exposure to maternal smoking during pregnancy.

"Prevention of child proteinuria is important since child proteinuria can lead to development of chronic kidney disease in adulthood and ultimately end stage renal disease," Kawakami said.

The findings is forthcoming in the Clinical Journal of the American Society of Nephrology (CJASN).