The evil effects of tobacco on the health of those who smoke it have been emphasized broadly in the past few years, both in the public and in the medical press. The possible damage that can be done to those who are "passive" smokers has also been pointed out. Now the fetus is in the front row of these. That is why it is important to point out this fact. After a brief statement about the physio-pathology of the condition the authors review the literature and extract the following points which can be ascribed to the use of tobacco: -- lowering of the birth weight; -- considerable increase in risk of premature separation of the placenta; -- a negative correlation with the frequency of pre-eclamptic toxaemia. The authors point out the additional feature that the effect of tobacco can potentiate the effects of an associated pathological condition. Finally, they emphasize the methodological difficulties which account for the numerous discrepancies and uncertainties that still exist about the action of tobacco on pregnancy.