Smoking during pregnancy found to increase risk of cleft lip and palate

March 27, 2000

ANN ARBOR, Mich. - Women who smoke while pregnant are 50 percent to 70 percent more likely than nonsmokers to give birth to a baby with a cleft lip or palate, according to a new study by researchers at the University of Michigan Health System.

The risk of the disfiguring facial birth defect rises with the number of cigarettes that a mother-to-be smokes each day, even after factors like the mother's race, age and educational level are considered. The finding, based on the largest-ever examination of cleft lip and palate incidence nationwide, suggests that the deformity should be added to the list of potential harmful effects from smoking during pregnancy. It also suggests a possible cause for the mysterious defect.

The results were recently published in the journal Plastic and Reconstructive Surgery.

"Not only can smoking cause prematurity and low birth weight, we now believe it can cause this devastating problem as well," says co-author Kevin Chung, M.D., M.S., a U-M plastic and reconstructive surgeon. "More than 13 percent of the 3.9 million women in this study said they smoked, which is troubling by itself, but this new evidence makes it even more so."

Adds co-author Steven Buchman, M.D., director of the Health System's Craniofacial Anomalies Program, "There are all sorts of reasons not to smoke anyway and this just adds another very important one in the prenatal and newborn care of the child. Cleft lip and palate make a huge difference in a child's life, and anything that can be done to reduce the risk is well worth it."

Cleft lip and palate are fairly serious birth defects. They are the fourth most common congenital abnormalities, affecting about one in 700 newborns. As their names suggest, the deformities are marked by obvious gaps in either the lips and nose or the roof of the mouth, due to incomplete fusing. Besides affecting a child's appearance, cleft lip and palate hinder the ability to breathe, eat, hear and speak. Correcting the defects involves many successive operations and years of therapy, but can still leave behind scars, speech impediments and emotional damage.

Chung and Buchman have seen the effects directly in their work: More than 100 cases of cleft lip and palate repair and related procedures are seen at the U-M each year. The U-M's multidisciplinary program is one of the largest and oldest in the nation.

Besides plastic and reconstructive surgeons Buchman and Chung, the U-M Craniofacial Anomalies Program includes 47 specialists and health professionals, including dentists, neurosurgeons, oral and maxillofacial surgeons, orthodontists, otolaryngologists, speech and language pathologists, social workers, geneticists, nutritionists, and pediatricians. The program was started in 1955 and aims to treat both the physical and psychological needs of each patient. Even with multidisciplinary care, the authors say the condition is not easy to treat.

"Cleft lip and palate definitely change a child's quality of life for the worse," says Chung. "Even though we can fix the external appearance, and we can also fix some of the internal deformities, their speech will always be quite different. They'll require as many as 10 to 20 surgeries throughout their life and the scar will always be there in the face."

The researchers embarked on the study in an attempt to provide more definitive information about a suspected possible connection between smoking and cleft lip and palate. Prior research elsewhere on smaller samples of newborns yielded conflicting results.

They gathered their statistics from the 1996 U.S. Natality Database, compiled by the National Center for Health Statistics of the Centers for Disease Control and Prevention. The database includes information compiled by physicians and nurses on each baby, as well as answers from new mothers to questions about their education, lifestyle and medical history. The 1996 data included 3,891,494 live births in all 50 states, and information on the pregnancy smoking habits in all states except California, Indiana, South Dakota and New York (excepting New York City).

Of the births in states with smoking data, 2,207 babies were recorded as having cleft lips, palates or both. Chung and Buchman took a random representative sample of 4,414 babies born without birth defects, and compared the smoking habits of the babies' mothers.

They found that overall, any cigarette use during pregnancy raised the risk of cleft lip or palate 55 percent. Mothers-to-be who smoked half a pack of cigarettes or less a day had a 50 percent higher risk, while those who smoked more than a pack a day had a 78 percent higher risk.

When they examined the data further, they found that certain other characteristics in the mother or the baby seemed to increase the chance of cleft lip or palate. Baby boys and underweight babies born to smoking mothers had an increased incidence. So did babies born to mothers who smoked and had either diabetes, high blood pressure during pregnancy or less than a high school education. Finally, mothers who were not African American or who were less than 27 years old were more likely to give birth to a child with a cleft palate or lip.

After correcting for all these factors, they still found that smokers were 30 percent more likely to have a child with the birth defect, and that the rate was still highest among those who smoked the most cigarettes.

The researchers also compared smoking data for mothers of the babies with cleft lips and palates, and those whose infants had other birth defects. This allowed them to correct for any under- or over-reporting of mothers' smoking habits due to guilt for smoking during pregnancy or, conversely, any vested interest in finding a cause for their baby's problem. Again, the mothers in the cleft lip and palate group were 37 percent more likely to smoke.

In all, the authors say, their study reinforces the importance of educational campaigns to dissuade women from smoking while pregnant.

Just as public health messages about the risks of drinking alcohol during pregnancy have resulted in a steady decline in fetal alcohol syndrome, they hope women will take heed of their results and others that have found smoking can harm a developing baby.

University of Michigan Health System

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