Looks like it\’s not as bad as we are told:
The report uses data from the UK National Child Development Study, which provides details of mothers and their children between 1973 and 2000 — a total of 3,368 women and 6,860 children.
The information includes the mothers’ smoking habits, information about their families, and the birthweight and gestation period of the children.
Analysis of the data shows that smoking throughout pregnancy reduces birthweight by 5.6 per cent, and the gestation period by just over a day. But when the results are corrected for other factors, such as diet, lifestyle and alcohol, the effect of smoking on birthweight drops to 1.8 per cent and the reduction in gestation becomes insignificant.
A rule of thumb from many years ago: each cigarette smoked per day reduced, on average, the birth weight by 5 grammes. As a healthy baby is in the 2.5-3 kg range, 10 fags a day reduces birth weight by what, 2%?