Tobacco, effect on fetus

Tobacco smoking during pregnancy causes fetal hypoxia and morphologic changes in the placenta (eg, placenta previa, placental abruption) and premature rupture of the membranes. These adverse effects result in an increased risk for intrauterine growth restriction, preterm birth, and in some cases, late fetal demise. Maternal smoking also is associated with increased risks for postneonatal morbidity and mortality, including poor lung development, asthma, respiratory infections, and sudden infant death syndrome.

Because approximately 15% to 20% of women smoke during pregnancy, this exposure is a major risk factor for pregnancy complications. Some studies have demonstrated that tobacco smoking is responsible for 15% of all preterm births and 20% to 30% of all infants of low birthweight. Therefore, cigarette smoking is one of the most important and  modifiable risk factors associated with adverse perinatal outcomes.

Tobacco smoking has not been shown to be associated with structural abnormalities such as hydronephrosis or talipes equinovarus. The growth retardation found in infants of mothers who smoked during pregnancy usually is asymmetric, with sparing of the head (ie, normal head circumference). Although chronic lung problems in the infant are associated with maternal smoking, respiratory distress syndrome occurs only in the context of preterm birth and is not a direct result of the tobacco exposure.

References:
Adams EK, Melvin CL. Costs of maternal conditions attributable to
smoking during pregnancy. Am J Prev Med. 1998;15:212-219
Cnattingius S, Nordstrom ML. Maternal smoking and feto-infant
mortality: biological pathways and public health significance. Acta
Paediatr. 1996;85:1400-1402