**3. Effects of tobacco smoking on progeny**

The birth defects among the offspring of smoking parents are high [127]. During their pregnancy, smoking woman showed an increased risk of trisomy 21 in the offspring, which results from maternal meiotic nondisjunction [128].

Maternal smoking increased the risk of spontaneous abortion, fetal growth restriction, preterm birth, stillbirth, and low birth weight [129]. A dose–response relationship was found between the risk of low-birth weight and the number of cigarettes smoked daily during pregnancy [129].

Maternal smoking was suggested to have even negative effects on the sperm count of men, whose mothers had smoked more than 10 cigarettes daily, in comparison to men having nonsmoker mothers.

Benzo[a] pyrene and nicotine in cigarette smoke have recently been shown to induce harmful alterations of sperm DNA that can be transmitted through the germ line to future generations [130, 131].

It has also been reported that preconception paternal tobacco smoking increases the chances and risk of multiple forms of morbidities in the fetus and offspring, which could be mediated through epigenetic modifications [132].

Kataoka et al. showed that the high number of daily cigarettes can be the reason behind the low weight at birth. Smoking mothers, who smoked 11–40 cigarettes/ day, had infants with 435 g lower weight in comparison with infants born to nonsmoking women. The same was observed for infants whose mothers smoked 6–10 cigarettes/day. Their birth weight was 320 g lower than infants of nonsmoking mothers [133].

Liu et al. concluded also that low number of cigarettes smoked during either the first or second trimester of pregnancy, even as low as 1–2 cigarettes per day, showed an association with a high risk of preterm birth. This proves that during pregnancy, there is no safe level or safe trimester for maternal smoking [134].
