Children of mothers who smoke during pregnancy can have cardiovascular or urogenital abnormalities along with birth defects. Earlier researches have shown that smoking during pregnancy increases her child’s risk for Sudden Infant Death Syndrome, also known as SIDS or cot death.

Recent study showed one more adverse effect of smoking during pregnancy. The study was conducted by Gary M Shaw's California group along with colleagues from Norway, The Netherlands, and Texas.

Smoking during pregnancy doubles the risk of a cleft palate or lip birth defect in the children. Children with oral clefts often have difficulty in feeding, frequent ear infections, hearing loss, speech difficulties, and dental problems. Researchers measured cotinine level, a metabolite of nicotine, in the blood from about 500 pregnant women. Researchers found that children born to mothers who smoked while pregnant were nearly 2.5 times more likely to have oral cleft defects, clefts that occur in the lip and palate (roof of the mouth)

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, California said: "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."