Before they even know they’re pregnant, women can trigger a gene causing a common birth defect just by smoking, a study found.
Children of mothers who smoke were more likely to have oral clefts than the children of non-smokers, according to a Johns Hopkins University study of 467 children born in Maryland between 1984 and 1992.
Cleft lips or palates, where the upper lip or the roof of the mouth do not close properly, occur during early fetal development, often before women know they are pregnant, said Terri Beaty, a researcher involved in 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,” Beaty said.
Of the study’s subjects, 183 had oral clefts while the remaining 284 - a control group - reflected the general population.
Children who carried the gene responsible for the defect and had smoking mothers were six times more likely to develop a cleft than the children in the control group, said Sharon Rippey, a spokeswoman for the Johns Hopkins School of Hygiene and Public Health.
Children who carried the gene and had non-smoking mothers were 1.2 times more likely to have the defect.
Oral clefts are among the most common birth defects. The split in the lip or palate can be corrected surgically.
The genotype responsible for the birth defect is present in 13.5 percent of the population, the researchers said.
Data for the study, published in Saturday’s issue of the American Journal of Epidemiology, was taken from the Maryland Birth Defects Reporting and Information System.
Doctors for many years have told pregnant women to avoid smoking, which has been linked to under-weight babies.