Smoking is disadvantageous for health in every respect. This is a fortiori the case during pregnancy. Pregnant women who smoke burden their unborn child with a mixture of hundreds of tobacco combustion products, dozens of which have been proved to be harmful, apart from the negative influence of the smoke induced blockade of the haemoglobin by carbon monoxide. Since the embryonic and foetal tissues which are formed in a short period, are particularly vulnerable, many detrimental effects can be observed. The fertility rate of women who smoke is reduced and their risk of abortion, miscarriage and preterm delivery is increased. Babies born to women who smoked during pregnancy have lower birth weights and are less developed. They run an increased risk of many disorders including asthma and even cancer. Their cancer risk seems even to be increased in adulthood. Smoking fathers also damage the development of their unborn child.