Smoking during pregnancy: foetal growth retardation and other risks for the newborn

In spite of the well-known effect of tobacco on embryo growth retardation, of the higher perinatal mortality of the offspring of smoking mothers, and of the dependence of perinatal mortality risk on small birth weight, it has consistently been found that small infants of smoking mothers have lower mortality rates than small infants of non-smoking mothers. This problem was studied on the perinatal database of a hospital, using adverse outcomes (death or Apgar score <7 at the 10th minute of life) as endpoints rather than perinatal or foetal mortality. A stochastic model constructed to account for cause-effect relations demonstrated that tobacco influences weight and mortality by independent pathways. Furthermore, this model shed some light on the non-tobacco determinants of small birth weight and neonatal morbidity. The method undertaken, based on the use of latent variables, had the advantage of analysing the prevalence, consequences and interactions of some risk factors without identifying them.