Fetal Alcohol Syndrome
There are several suggested diagnostic schemas for FAS (e.g., Bertrand et al., 2004 ; Chudley et al., 2005 ; Hoyme, 2005) and, while there are minor differences between them, all require anomalies in three distinct areas: (i) prenatal and postnatal growth deficits; (ii) facial dysmorphology; and (iii) central nervous system (CNS) dysfunction. Typically, growth retardation is defined as evidence of prenatal or postnatal weight or height at or below the 10th percentile, after correcting for age, gender, race, and other appropriate variables.
The Canadian guidelines also recommend evidence of a disproportionately low weight-to-height ratio at or below the 10th percentile. Most guidelines recommend three essential dysmorphic features – a smooth philtrum, a thin upper vermillion border, and small palpebral fissures – although the revised Institute of Medicine (IOM) guideline requires only two of the three characteristics (Hoyme et al., 2005). Finally, a diagnosis of FAS requires evidence of CNS abnormality. Within this criterion, the diagnostic schemas differ more substantially.
For example, the revised IOM guideline only requires evidence of structural brain abnormalities, such as diminished head circumference at or below the 10th percentile. The CDC criteria are more extensive, outlining structural, neurological, and functional CNS dysfunction. Structural anomalies may be evidenced by the two criteria delineated in the IOM guidelines, as well as brain abnormalities observed with neuroimaging techniques. Seizures or other signs of neurological damage not attributable to postnatal insult may qualify as evidence of neurological problems.
Lastly, functional abnormalities are defined as a global cognitive deficit (such as a decreased IQ), or deficits in three different functional CNS domains, which include cognition, behavior, executive functioning, and motor functioning. The Canadian guidelines outline eight domains that must be assessed: hard and soft neurologic signs; brain structure; cognition; communication; academic achievement; memory; executive functioning and abstract reasoning; and attention deficit/hyperactivity. Diagnosis requires evidence of impairment in three of these domains.
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.
Fetal Alcohol Spectrum Disorder(s)
It is now recognized that there is a spectrum of deficits arising from PAE; FASD is the umbrella term used to describe this broad range of outcomes. Since the term FASD is not diagnostic, some of the guidelines (Chudley et al., 2005 ; Hoyme et al., 2005) use the terms ARND or ABRD (alcohol-related birth defect) to describe these FASDs. ARBD is a term which refers to individuals with a confirmed history of PAE and who display congenital birth defects, such as physical malformations or organ abnormalities. The ARND classification refers to individuals with a confirmed history of PAE who have behavioral and cognitive deficits related to CNS dysfunction. For example, an association between maternal alcohol use and sudden infant death syndrome (SIDS) has been suggested (e.g., Burd and Wilson, 2004).
This would make SIDS an FASD in those cases where PAE was suspected, if other causes could be ruled out. Similarly, an increased risk of congenital heart defects has been associated with prenatal alcohol exposure; thus, such heart defects might be considered an FASD/ARBD if the mother drank heavily during pregnancy. Behavioral problems in children exposed to alcohol in utero, but who do not meet the diagnostic criteria of FAS, are perhaps the most commonly cited type of FASD/ARND.
Mortality/Morbidity
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.
Race
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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Tanya T. Nguyen, Jennifer Coppens, and Edward P. Riley
Edited by Edward P. Riley, Sterling Clarren, Joanne Weinberg, and Egon Jonsson
Tanya T Nguyen practices as a Pediatrician in Alhambra, CA.
Jennifer Coppens, Medical Student, University of Alberta
Prof. Dr. Edward P. Riley San Diego State University Center for Behavioral Teratology
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REFERENCES
- Abel, E.L. (1999) Was the fetal alcohol syndrome recognized by the Greeks and Romans? Alcohol Alcohol., 34 (6), 868 – 872.
- Adnams, C.M., Sorour, P., Kalberg, W.O., Kodituwakku, P., Perold, M.D., Kotze, A., September, S., Castle, B., Gossage, J., and May, P.A. (2007) Language and literacy outcomes from a pilot intervention study for children with fetal alcohol spectrum disorders in South Africa. Alcohol, 41 (6), 403 – 414.
- Barry, K.L., Caetano, R., Chang, G., DeJoseph, M.C., Miller, L.A., O’ Connor, M.J., Olson, H.C., Floyd, R.L., Weber, M.K., DeStefano, F., Dolina, S., Leeks, K., and National Task Force on Fetal Alcohol Syndrome and Fetal Alcohol Effect (March 2009) Reducing Alcohol - Exposed Pregnancies: A Report of the National Task Force on Fetal Alcohol Syndrome and Fetal Alcohol Effect, Centers for Disease Control and Prevention, Atlanta, GA.
- Bertrand, J. (2009) Interventions for children with fetal alcohol spectrum disorders (FASDs): overview of findings for five innovative research projects. Res. Dev. Disabil., 30 (5), 986 – 1006.