Parental smoking. Its effects on fetus and child health.

Smoking is a risk factor in pregnancy. Maternal smoking reduces the birthweight by 150-250 g (dose-response relationship), shifting the birthweight (and length) distribution to the left. Reduction of birthweight without shortening of gestation creates a group of small-for-date babies. Intrauterine hypoxia seems responsible for the growth retardation in smokers' babies as in babies of mothers living at high altitudes. Cigarette smoking of the mother affects fetal oxygenation, due to high levels of COHb in the blood of both mother and child. This observation is strongly supported by animal experiments. The total of (abortions), stillbirths, early and late neonatal mortality (especially stillbirths) is higher in babies of smoking than in those of nonsmoking mothers and highest among the poor. Approximately 5% of all stillbirths and neonatal deaths must be attributed to the increased mortality risk for the infant of mothers who smoke during the second half of pregnancy. Pregnancies of smoking mothers show about the same increase in infant wastage as pregnancies at high altitudes. The babies of smoking mothers show little excess of congenital malformations, if any. The placenta coefficient is increased. This symptom of compensatory placental hypertrophy cannot avert some impairment of fetal nutrition. There is less preeclamptic toxemia in smokers than in nonsmokers, but a higher incidence of antepartum hemorrhage and placental separation. Concerning long-term effects, smoking during pregnancy seems to be associated with a slight impairment of mental and physical growth. When the mother is nonsmoker and the father smokes more than ten cigarettes daily, an increase in perinatal mortality seems probable. Smoke aggravates the asthma of children in about two-thirds of those whose parents smoke. Healthy children of smokers are sick more frequently (primarily respiratory illness) than those of nonsmokers. Smoking parents and teachers stimulate their children and pupils to start smoking. Once smokers children may remain smokers. From the polemics on cause (smoking) and association (smoker) regarding the effects of parental smoking on the health of the fetus, the conclusion must be that health workers involved in obstetrics have great responsibilities in the antismoking campaign.