Fetal Alcohol Syndrome
- Author: Keith K Vaux, MD; Chief Editor: Ted Rosenkrantz, MD more...
Adverse fetal, neonatal, and pediatric effects occur with maternal alcohol consumption during pregnancy. The diagnosis of fetal alcohol syndrome (FAS) is based on findings in the following 3 areas: (1) characteristic facial anomalies (see image below), (2) growth retardation (intrauterine growth restriction and failure to have catch-up growth), and (3) CNS involvement (cognitive impairment, learning disabilities, or behavioral abnormalities).
Prenatal exposure to alcohol is associated with a variable spectrum of effects referred to as fetal alcohol spectrum disorders (FASD), with fetal alcohol syndrome at the most severe end of that spectrum. Children with fetal alcohol syndrome disorder may have clinically significant CNS involvement but few or no characteristic physical features.
Lemoine et al first described the pattern of malformation associated with heavy prenatal alcohol exposure in France in 1968, and Jones and Smith first described it in the United States in 1973. Prenatal alcohol exposure is of substantial public health concern for the following reasons: (1) FAS is the leading known cause of mental retardation, (2) fetal alcohol syndrome or fetal alcohol syndrome disorder is associated with persistent physical and neurodevelopmental abnormalities, and (3) fetal alcohol syndrome disorder crosses all socioeconomic groups and affects all races and ethnicities. The costs for 1 child with fetal alcohol syndrome are estimated to be $2 million over a lifetime, and costs of fetal alcohol syndrome to the American taxpayer are more than $321 million each year.
Alcohol crosses the placenta and rapidly reaches the fetus. Extensive studies have demonstrated equivalent fetal and maternal alcohol concentrations, suggesting an unimpeded bidirectional movement of alcohol between the 2 compartments. The fetus appears to depend on maternal hepatic detoxification because the activity of alcohol dehydrogenase (ADH) in the fetal liver is less than 10% of that observed in the adult liver. Furthermore, the amniotic fluid acts as a reservoir for alcohol, prolonging fetal exposure.
The mechanism for the spectrum of adverse effects on virtually all organ systems of the developing fetus is unknown. Ethanol and its metabolite acetaldehyde can alter fetal development by disrupting cellular differentiation and growth, disrupting DNA and protein synthesis and inhibiting cell migration. Both ethanol and acetaldehyde modify the intermediary metabolism of carbohydrates, proteins, and fats. Both also decrease the transfer of amino acids, glucose, folic acid, zinc, and other nutrients across the placental barrier, indirectly affecting fetal growth due to intrauterine nutrient deprivation. Elevated levels of erythropoietin in the cord blood of newborns exposed to alcohol are reported and suggest a state of chronic fetal hypoxia.
Studies have shown that prenatal alcohol exposure affects the hypothalamic-pituitary-adrenal (HPA) axis as well as alters basal and poststress cortisol levels. In a Canadian study involving 26 children (aged 6-14 y) and 32 control children, Keiver et al found significantly elevated cortisol levels in the afternoon and at bedtime in those with known high prenatal exposure to alcohol (alcohol exposure rank 4) relative to those with low/unknown levels of prenatal alcohol exposure (alcohol exposure rank 3) and the control group. The investigators suggest these findings provide evidence for HPA dysregulation due to chronic fetal alcohol exposure, which may lead to long-term psychologic and medical morbidity.
Although careful comprehensive studies have not been performed and though passive surveillance systems are inadequate to measure the incidence of fetal alcohol syndrome or fetal alcohol syndrome disorder, the incidence of fetal alcohol syndrome in the United States is estimated to be 1-2 cases per 1000 live births. The incidence is related to the population studied, with highest incidence reported in areas where heavy drinking during pregnancy is common and where attention to diagnosis is greatest.
To date, no comprehensive population-based study with careful and standardized diagnostic methods applied to a large, representative sample of children has been performed. Likewise, the incidence of the broad spectrum of fetal alcohol syndrome disorder has not been well studied. However, data in one sample demonstrated that approximately 1 in 100 children have alcohol-related effects.
Among the subset of high-risk pregnant drinkers, estimated incidences of fetal alcohol syndrome differ because of variable definitions of heavy drinking and inconsistent methods of diagnosis. Therefore, rates range from 4% to as much as 44%.
Estimated rates of fetal alcohol syndrome in international settings are sparse in the literature. They are based on variable definitions and methods of ascertainment and range from 1 in 1000 to less than 1 in 10,000 live births. However, in some extremely high-risk areas, such as selected communities in South Africa where binge drinking in pregnancy is relatively common, careful in-school assessments have shown that rates of fetal alcohol syndrome may be as high as 4-5% of all children in the normal first grade in school.
Adverse effects on the outcome of pregnancy, in addition to fetal alcohol syndrome disorder, have been noted with chronic or heavy alcohol use. These effects include an increased risk for spontaneous abortion, placental abruption, preterm delivery, amnionitis, stillbirth, and sudden infant death syndrome.
Commonly associated factors, such as maternal tobacco or other substance abuse, low socioeconomic status, and poor nutrition, complicate the morbidity and mortality associated with prenatal alcohol exposure.
Regardless of race or ethnicity, fetal alcohol syndrome and fetal alcohol syndrome disorder occur in women who drink heavily during pregnancy. Rates of fetal alcohol syndrome appear to be highest among groups of low socioeconomic status. What is unknown is how these findings are related to a high prevalence of risky drinking in some populations; compromised nutritional status or general health; and, therefore, reduced resiliency to the effects of alcohol, possible genetic susceptibility, or a combination of these and other factors.
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