Alcohol
Maternal alcohol ingestion during pregnancy may result in a recognizable pattern of congenital anomalies known as fetal alcohol syndrome. Fetal alcohol syndrome features include prenatal and postnatal growth restriction, characteristic facial anomalies (ie, short palpebral fissures, microphthalmia, indistinct or absent philtrum, thin upper lip, midfacial hypoplasia), microcephaly, joint contractures, and cardiac defects. Fetal alcohol syndrome is associated postnatally with mental retardation, hyperactivity, and developmental delays. Alcohol abuse during pregnancy is a leading cause of mental retardation. Maternal alcohol abuse is also associated with an increased risk of spontaneous abortion.
It is difficult to correlate the amount of alcohol consumed to the risk of fetal alcohol syndrome. Among pregnant women who consume four or more drinks per day during pregnancy, the risk for fetal alcohol syndrome may be as high as 20%, with risks increasing to perhaps 40% with six drinks per day. Women who have eight or more drinks per day are at significant risk (perhaps 60% or higher) for giving birth to an infant with fetal alcohol syndrome. The American Medical Association has stated that any woman who consumes four or more alcoholic drinks per day during pregnancy is significantly endangering the health of her unborn child. One beer, one shot of liquor, one mixed drink, and one glass of wine all contain the same amount of alcohol, approximately 0.5 oz of absolute alcohol. Thus, all forms of alcohol are equally hazardous. Risks associated with binge drinking are unknown but are likely to be substantial. No quantifiable risk has been associated with an occasional alcoholic beverage during pregnancy, but prudent medical advice is for pregnant women to avoid alcohol consumption completely.
Drugs and Chemicals Associated with Birth Defects
Tobacco
Smoking tobacco poses a threat to reproductive function and pregnancy outcome in women. The prevalence of smoking among adults has decreased from approximately 40% in 1965 to approximately 25% in the 1990s, with a similar decrease among women of reproductive age.
Stop smoking
The pregnant smoker may be at increased risk for the spontaneous abortion of an otherwise normal fetus, fetal death associated with placental abruption or placenta previa, preterm delivery, and PROM. A dose-response relationship has been shown between the amount of maternal smoking and reduced birth weight. The offspring of women who smoke approximately 20 cigarettes (one pack) per day during pregnancy have birth weights that are approximately 200 g less than those of infants born to women who do not smoke. If a woman stops smoking during the last 4 months of pregnancy, the risk of delivering a baby with lowered birth weight is similar to that of a nonsmoker. The use of smokeless tobacco also increases blood nicotine levels to levels comparable to those associated with cigarette smoking and, based on limited data, may result in similarly decreased birth weight. The possible clinical effects of passive smoking during pregnancy have not been clearly established.
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