Women who smoke during pregnancy have a greater chance to have children with damage to the kidneys than mothers who steer clear of cigarettes, a study suggests.
Smoking during pregnancy has long been linked to preterm and underweight babies, and a wide range of congenital anomalies. The current study provides new evidence that the kidneys are among the organs at risk for damage, said lead author Dr. Maki Shinzawa, public health, researcher at the University of Kyoto in Japan.
“The smoking of cigarettes releases nicotine and other harmful or potentially harmful substances, such as nitrogen oxides, polycarbonate, and carbon monoxide, some of which cross the placenta,” Shinzawa said by e-mail. “Some of these trans-placental substances may affect foetal programming of the kidney during the pregnancy.”
Shinzawa and colleagues examined the data from the urine tests of 44,595 children to look for elevated levels of protein in the urine, which may indicate impaired renal function.
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Data on maternal smoking was collected from women in the prenatal controls, and the researchers also had the records of their children with the health of the controls on a four, nine, 18 and 36 months old.
Overall, 79 percent of the women said that they had never smoked and a further 4 percent said they stopped smoking during pregnancy. About 17 percent of the mothers said that they continue to smoke while they were pregnant.
The absolute risk of damage to the kidneys among the children was low. But in comparison with children born to non-smoking mothers, children whose mothers smoked during pregnancy were 24 percent more likely to show signs of damage to the kidneys in the urine tests by the age of three.
The Urine tests showed elevated protein levels in 1.7 percent of children born to smokers, 1.6 percent of the children whose mothers were ex-smokers and 1.3 per cent of the children born to women who never smoked.
Children exposed to second-hand smoke in the home, but also were shown to have a higher risk of kidney disease than children who did not live with smokers, but the difference was not great enough to exclude the possibility that it was due to chance.
A limitation of the study is the dependence of women to accurately report and remember how much they smoked before or during pregnancy, and a lack of lab tests to confirm smoke exposure, the authors note in the Clinical Journal of the American Society of Nephrology.
Still, the findings add to the evidence that smoking damages the kidneys, a connection that is already previous research has established adult smokers and children who breathe second-hand smoke, said Dr. Paul Fowler, director of the Institute for Medical Sciences at the University of Aberdeen in the united kingdom.
“Maternal smoking has been observed to lead to a decreased kidney size in the offspring, which is important because it is known that retarded kidney development contributes to (high blood pressure) and renal injuries in adults,” Fowler, who was not involved in the study, added by e-mail.
“This study highlights one more reason why women should not smoke during pregnancy and why children should be brought up in a cigarette-free households,” said Fowler. “It is not, in itself, an overwhelming reason, but rather another nail in the coffin.”