Smoking during pregnancy doubles risk that baby will be born with a cleft lip or cleft palate.

Babies whose mothers smoked during pregnancy were more than twice as likely to have a cleft palate or lip as those whose mothers didn’t, according to research results released today.

Although the study confirms earlier findings, it is unique because it did not rely on women’s self-reported smoking habits during pregnancy. Instead, researchers used the more reliable method of measuring the levels of cotinine, a metabolite of nicotine, in the blood from about 500 pregnant women.

“This research is the first time we’ve been able to measure something – in this case cotinine – and determine the risk of smoking during pregnancy for oral-facial birth defects,” Gary M. Shaw, PhD, research director and senior epidemiologist of the March of Dimes California Research Division, Children’s Hospital Oakland Research Institute in Oakland, Calif.

Nearly 7,000 babies are born annually with an oral-facial cleft in the United States. Children with oral clefts often have difficulty feeding, frequent ear infections, hearing loss, speech difficulties, and dental problems. Surgery often can repair these birth defects, which typically occur by the seventh week of pregnancy.

“The message to women is simple and clear: Don’t smoke during pregnancy or even if you are considering becoming pregnant,” said Dr. Jennifer L. Howse, president of the March of Dimes. Cigarettes and pregnancy don’t mix - tobacco toxins are tragically harmful for the unborn baby.

“This research supports our 2008 Petition for Preemies, which calls on federal and state officials to include smoking cessation programs as part of maternity care. If we can help mothers quit smoking, we can help give more babies a healthy start in life,” Dr. Howse continued (Courtesy of EurekAlert!, a service of AAAS).

Reference: “Mid-Pregnancy Cotinine and Risks of Orofacial Clefts and Neural Tube Defects” will be published in The Journal of Pediatrics but is available November 5, 2008 online (DOI reference number: 10.1016/j.jpeds.2008.08.006).