A new study has come up with another reason for pregnant women not to smoke.
It seems that a mother's cigarette smoking increases the risk that her baby may be born with extra, webbed or missing fingers or toes.
According to a new study by doctors at the Children's Hospital of Philadelphia, although the overall risk of such abnormalities in fingers and toes is relatively low, just half a pack of cigarettes per day increases the risk to the baby by 29 percent, compared to non-smokers.
Because limbs develop very early in pregnancy, the effect may possibly occur even before a woman knows she is pregnant.
Benjamin Chang, M.D.,a pediatric plastic and reconstructive surgeon, the study leader and co-author Li-Xing Man, M.Sc., both of Children's Hospital and the University of Pennsylvania, reviewed the records of more than 6.8 million live births listed in the U.S. Natality database from 2001 and 2002.
This is one of the largest study of its kind, covering 84 percent of U.S. births.
The study population were placed into four groups: non-smokers; those who smoked one to ten cigarettes daily; 11 to 20 cigarettes daily; and 21 or more per day.
They found that women who smoked up to half a pack a day were 29 percent more likely to have babies with digital anomalies and women who smoked more than a pack of cigarettes a day during pregnancy were 78 percent more likely to have babies with digital anomalies.
The researchers found that of the total 6.8 million births, 5,171 children born with digital anomalies had mothers who smoked during pregnancy.
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.
It seems that 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 10 times more common in African-Americans and only slightly more common in boys.
The majority of isolated congenital digital anomalies occur spontaneously without any family history.
It was the increased number of cases involving these diagnoses in their own practices, that led the researchers to investigate environmental factors that might be associated with these conditions.
Dr. Chang says there is a strong indication that higher exposure is linked to higher risk, and though that risk is small, tobacco exposure has the potential to affect thousands of children.
He says health professionals should increase their efforts to remind women of the dangers of smoking.
The study is published in the January issue of Plastic and Reconstructive Surgery.