Yet another study among Norwegian mothers showing that smoking during pregnancy is not a good idea: apparently, smoking during the first trimester of pregnancy is clearly linked with an increased risk of cleft lip in babies.

There was little evidence of an effect of smoking on the risk of cleft palate alone. However, for cleft lip (with or without cleft palate), there was an increased risk, almost two-fold when the mother smoked over 10 cigarettes per day and a 1.6 fold risk from passive smoking (defined as being within 2 metres of a smoker for 2 hours a day). The researchers estimate that 19 % of cases of cleft lip in Norway may be due to maternal smoking in the first trimester.

Based on these results, it seems to be a sensible idea not only for a pregnant woman to quit smoking, but also to avoid passive smoke coming from people in the household, workplace, etc.