An English study dealing with the impact of smoking on people's health, worked with the data of 5,451 fathers who smoked. Among them was a group of 166 fathers who smoked just before puberty, at age 11, the period when sperm begin to form in males, which later transfer from the father's genetic material to their children. They left their sons an undesirable inheritance - obesity. The sons were more obese than average and even more obese than the sons of men who smoked but not at that critical stage of puberty. The impact on the daughters has not yet been confirmed. Cigarette smoke, both from active smoking and the passive inhalation of cigarette smoke, is one of the best-described toxic substances affecting pregnant women. The effects of cigarette smoke result in an increased risk of low birth weight, asthma, obesity, and type II diabetes. A study including a large number of existing studies, called a meta-analysis, has demonstrated a direct association between smoking and the incidence of cancer of the nervous system (brain and central nervous system) in children. However, in addition to cancers, smoking is also associated with placental insufficiency and preterm birth as well as being a risk factor for sudden infant death syndrome. The fact that a woman's smoking has an undeniable negative effect on the child is also evidenced by the fact that the by-products of tobacco combustion have been detected not only in the breast milk of smoking mothers but also in the blood of the foetus and the mother of the newborn.