Gene, Smoking Link Established In Cleft Palates


By Lisbeth Pettingill

     Even before a woman knows she is pregnant, her smoking can
trigger a specific gene in the unborn baby to produce a common
birth defect, isolated cleft palate, according to a recent study
by researchers at the Johns Hopkins University School of Public
Health. The genotype itself appears in approximately 13.5 percent
of the population.

     Their study, published in the April 1 issue of the "American
Journal of Epidemiology," showed a significant association
between the baby's genotype for a particular growth factor
(transforming growth factor alpha, or TGFA) and risk of cleft
palate (where the roof of the mouth does not close properly
during early fetal development) when the mother smoked. Babies of
mothers who did not smoke showed no difference in risk whether
they carried the gene or not.  

     "This is the first evidence that women who smoke are also
placing their unborn children at risk based on the baby's genes,"
said Terri Beaty, professor of epidemiology at the School of
Public Health and senior author of the study. "Since this birth
defect occurs very early in pregnancy and since it is the baby's
genes that determine risk, this is one more reason for all women
of reproductive age to avoid smoking," she added. 

     The study involved infants with isolated birth defects,
consisting of 69 cleft palate-only cases, 114 cleft lip with- or
without-palate cases and 284 controls with non-cleft birth
defects, all born in Maryland from 1984 to 1992. Data for the
study came from the Birth Defects Reporting and Information
System operated by the Division of Hereditary Disorders of the
Maryland Department of Health and Mental Hygiene.

     Oral clefts, including cleft palates, are among the most
common birth defects, averaging one per 1,000 live births among
Caucasians. Most cases occur as isolated birth defects.