Background: The U.S. Natality database from 2001 and 2002 was used to investigate the relationship between maternal cigarette smoking during pregnancy and the risk of having a child with polydactyly, syndactyly, or adactyly.
Methods: The records of 6,839,854 live births were examined to identify 5171 newborns with isolated polydactyly, syndactyly, or adactyly and 10,342 controls with no congenital anomalies.
Results: Maternal cigarette use during pregnancy was associated with a significantly elevated risk of having a child with a congenital digital anomaly (unadjusted odds ratio, 1.33; 95 percent confidence interval, 1.21 to 1.47; p < 0.0001). Univariate analysis indicated that maternal marital status and medical risk factors (anemia, cardiac disease, lung disease, diabetes, hydramnios/oligohydramnios, pregnancy-associated hypertension, incompetent cervix, previous preterm or small-for-gestational-age infant, and rhesus factor sensitization) were potential confounding factors. After adjustment for these variables, the odds ratio remained significant (adjusted odds ratio, 1.31; 95 percent confidence interval, 1.18 to 1.45; p < 0.0001). Cigarette consumption per day was divided into four groups: no smoking, 1 to 10 cigarettes per day, 11 to 20 cigarettes per day, and 21 or more cigarettes per day. A statistically significant dose-response relationship was found when comparing each smoking category with the no-smoking reference group: 1.29 (95 percent confidence interval, 1.15 to 1.46), 1.38 (95 percent confidence interval, 1.12 to 1.71), and 1.78 (95 percent confidence interval, 0.97 to 3.26), respectively. Increased cigarette smoking during pregnancy resulted in an elevated risk of having a child with polydactyly, syndactyly, or adactyly.
Conclusions: This is the largest study to date to investigate specifically the association between maternal cigarette smoking and the risk of having a newborn with a congenital digital anomaly. The elevated odds ratio for tobacco use and the significant trend in the dose-response relationship suggests smoking during pregnancy may be an important preventable risk factor for these common congenital differences.