Half a pack of cigarettes per day increases the risk to the baby by 29 percent. Because limbs develop very early in pregnancy, the effect may occur even before a woman knows she is pregnant. “We found that the more a woman smoked, the higher the risk became that the baby would have these defects,” said study leader Benjamin Chang, M.D., paediatric plastic and reconstructive surgeon at The Children’s Hospital of Philadelphia.
Chang reviewed the records of more than 6.8 million live births listed in the U.S. Natality database from 2001 and 2002. It was the largest study of its kind, covering 84 percent of U.S. births. There was a statistically significant dose-response effect, with increased odds of having a newborn with a congenital digital anomaly with increased maternal cigarette smoking during pregnancy.
Digital anomalies include polydactyly (presence of more than five fingers or toes on a hand or foot), adactyly (the absence of fingers or toes) and syndactyly (fused or webbed fingers or toes). Limbs begin to develop between four and eight weeks of gestation and advance from a tiny nub to nearly-fully formed fingers and toes. Many women only discover they are pregnant during this period.
Missing digits are twice as likely to occur in boys and are more common in Caucasians than African Americans. More than five digits on hands and feet is ten times more common in African Americans and only slightly more common in boys. Nevertheless, the majority of isolated congenital digital anomalies occur spontaneously without any family history. The increased number of cases involving these diagnoses in their own practices led researchers to investigate environmental factors that might be associated with these conditions.
MEDICA.de; Source: Children's Hospital of Philadelphia