Recent studies take into account the sex of the offspring and racial and genetic background. With these factors accounted for, the reductions in birth weight of infants born to smoking mothers range from forty to four hundred and thirty grams less than the birth weights of children born to nonsmoking mothers, with the average being two hundred grams, or seven ounces, less. Also, smoking infants tend to be shorter than nonsmoking infants, approximately 1.4 centimeters shorter, though the major factor is the weight. In some studies, the circumference of the infant's head was significantly reduced, due to maternal smoking. The low birth weight is also affected by the amount of cigarettes smoked a day. Eight percent of women who smoke one cigarette a day have babies with a low birth weight. Infants born to mothers who smoked while they were pregnant tend to remain below normal in height and weight. The lower the birth rate of an infant is, the greater the chance of perinatal mortality, also logically brought about by maternal smoking. Spontaneous abortions in early pregnancies are usually associated with malformations and chromosomal aberrations in the developing fetus. A study was made by Naeye that death rates due to malformations increased when the mother smoked more than ten cigarettes a day. His study included 100 pregnant women who smoked ten cigarettes a day and 100 pregnant women who didn't smoke at all. The conclusion was the stillbirth rate of 1.72% for smoking babies as compared to 0.1% for nonsmoking babies. It was established that malformations due to maternal smoking triggered stillbirth. The fetus can also acquire a build-up of patent ductus arteriosus, which can cause cardiovascular abnormalities in the future. Also, babies born to smoking mothers are twice as likely to have congenital heart disease when they're older. The long-term effects smoking while pregnant can have on an infant can affect them for their whole life; in growth, respiratory disorders, and behavior.
