Smoking during pregnancy has long been linked to preterm and
underweight babies and a wide range of birth defects. The current
study offers fresh evidence that the kidneys are among the organs at
risk for damage, said lead author Dr. Maki Shinzawa, a public health
researcher at Kyoto University in Japan.
“Cigarette smoking releases nicotine and other harmful or
potentially harmful substances, such as nitrogen oxide,
polycarbonate, and carbon monoxide, some of which cross the
placenta,” Shinzawa said by email. “Some of these trans-placental
substances may affect fetal programming of the kidney during
pregnancy.”
Shinzawa and colleagues examined data from urine tests from 44,595
children to look for elevated levels of protein in the urine, which
can indicate impaired kidney function.
Data on maternal smoking was collected during women’s prenatal
checkups, and researchers also had records from their children’s
health checkups at four, nine, 18 and 36 months of age.
Overall, 79 percent of women said they never smoked and another 4
percent said they stopped smoking during pregnancy. About 17 percent
of the mothers said they continued to smoke while they were
pregnant.
The absolute risk of kidney damage among the children was low. But
compared with children born to nonsmoking mothers, kids whose
mothers smoked while pregnant were 24 percent more likely to show
signs of kidney damage in their urine tests by age three.
Urine tests showed elevated protein levels in 1.7 percent of
children born to smokers, 1.6 percent of kids whose mothers were
former smokers and 1.3 percent of children born to women who never
smoked.
Children exposed to second-hand smoke at home also appeared to have
a higher risk of kidney damage than kids who didn’t live with
smokers, but the difference wasn’t big enough to rule out the
possibility that it was due to chance.
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One limitation of the study is its reliance on women to accurately
report and recall 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 evidence linking smoking to kidney
damage, a connection that some previous research has established for
adult smokers and for children who inhale second-hand smoke, said
Dr. Paul Fowler, director of the Institute of Medical Sciences at
the University of Aberdeen in the UK.
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“Maternal smoking has been observed to lead to reduced kidney size
in offspring, which is of concern since it is known that retarded
kidney development contributes to (high blood pressure) and renal
injury in adults,” Fowler, who wasn’t involved in the study, added
by email.
“This study highlights one more reason why women should not smoke
during pregnancy and why children should be raised in cigarette-free
households,” Fowler said. “It is not, in itself, an overwhelming
reason, but rather one more nail in the coffin.”
SOURCE: http://bit.ly/2ihJDxI Clinical Journal of the American
Society of Nephrology, online December 7, 2016.
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