Maternal smoking and urinary organ malformations.

BACKGROUND In order to investigate whether an earlier reported association between maternal smoking during pregnancy and urinary organ malformations could be confirmed, a study was made using Swedish health registries. METHODS Infants with kidney malformations (n = 483) and infants with other urinary organ malformations with no primary involvement of the kidney(s) (n = 719) were selected among 1117021 infants born 1983-1993 with known smoking exposure in early pregnancy. RESULTS A moderate statistically significant association between maternal smoking and kidney malformations was found (adjusted odds ratio [OR] = 1.22, 95% confidence interval [CI] : 1.00-1.48). With the exception of genetic renal polycystic disease, the main subgroups of kidney malformations showed similar OR. For other urinary organ malformations, no association with smoking could be detected (OR = 0.93, 95% CI: 0.79-1.11). CONCLUSIONS This study supports an association between maternal smoking during pregnancy and kidney malformations. No obvious confounders were detected but further work is needed before a causal inference can be made.