Fetal Alcohol Syndrome
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By Maia Szalavitz
STATS Senior Fellow
29 April 2005 [Updated, August 2010]

Heavy drinking by mothers-to-be during pregnancy has been associated with birth defects and problematic behavior in children since antiquity. A passage in Judges (13:7) in the Bible says: "Behold, thou shalt conceive and bear a son; and now drink no wine or strong drinks." Aristotle wrote that "foolish, drunken and hare-brained women most often bring forth children like unto themselves, morose and languid."

However, "Fetal Alcohol Syndrome" (FAS) was not characterized in the medical literature until 1968, by Paul LeMoine of Nantes, France-and the diagnosis did not get widespread attention until 1973 when a paper by David Smith and Ken Jones of the University of Washington suggested specific criteria for its diagnosis.

Because research in this area has only begun so recently, many key questions remain unanswered. How exactly does alcohol cause damage to unborn children? How many affected infants are born each year? Will all children of women who drink heavily while pregnant be affected by alcohol-related damage in some way? Which women are at highest risk of having an affected child? And what about women who drink moderately-is there any safe level of consumption of alcohol during pregnancy? This guide will explore what we know-and what we don't-about problems associated with drinking during pregnancy.

A Guide Through the Alphabet Soup of Fetal Alcohol Spectrum Disorders

When fetal alcohol syndrome was first described, the diagnosis consisted of three primary groups of symptoms. These include a distinct set of facial features, which may include skin folds at the corner of the eye, smaller than normal head circumference, small opening area around the eye, short nose, thin upper lip and an absent or hard to detect philtrum (the indentation between the nose and upper lip). The second group of symptoms involves slower rates of physical development and growth, particularly of the head. The third group consists of neurological problems which can include lowered IQ, behavior problems, attention disorders, learning problems and difficulties with socialization.

But while FAS facial features have come to be associated with the most severe cases of the condition, researchers now believe that these simply mark significant alcohol exposure only early in pregnancy. Consequently, some affected people may have neurological defects just as severe as full FAS, but without the characteristic facial structure. Their development was most strongly affected by alcohol consumed at other points during pregnancy - which were just as damaging to brain growth, but did not affect the development of the face. Recent research suggests that people with the facial anomalies of FAS have more severely impaired cognitive function than those without them, but the correlations are not strong enough to use physical characteristics in children to predict later cognitive function. new footnote 1

At first, such people were defined as having Fetal Alcohol Effects (FAE), but this diagnosis was seen as too vague and too suggestive of the idea that these defects weren't as severe as FAS itself. As a result, the Institute of Medicine of the National Academy of Sciences, which advises Congress on medical controversies, decided in 1996 to label the full range of the disorder FASD-Fetal Alcohol Spectrum Disorder. They defined five categories of affected children.

These include those with the full facial features and known maternal alcohol exposure (FAS), those with these features but whose alcohol exposure in utero could not be determined (FAS without confirmed maternal exposure), those with some but not all of the facial features and known alcohol exposure in the womb (Partial FAS) and two new diagnoses. These are alcohol-related birth defects (ARBD), which include kidney, heart, eye and ear defects in the absence of FAS facial features; and alcohol-related neuro-developmental disorder (ARND), which involves brain defects, behavior problems and learning problems known to be associated with alcohol exposure in utero but without FAS-qualifying facial features. The latter two diagnoses can occur together and both require known maternal alcohol use.

True Number of FASD Cases Unknown
It is hard to get good estimates of how common FASD cases are. In some particularly vulnerable populations, such as certain Native American groups and some South African communities, full FAS is estimated to affect 10-40 infants per 1000 live births footnote icon.

A 2009 review of the research estimated the overall U.S. prevalence of FAS to be 2-7 cases per 1000 live births footnote icon - but CDC estimates are lower, .5 to 1.5 per 1000 live births footnote icon. Even the lower rate, however, makes FAS as common as Down syndrome.

Moreover, researchers estimate that for every one child with full FAS, there are at least 3 who have one of the other IOM diagnoses, which means that 1% of all children born in the U.S. may be affected footnote icon.

These are probably under-estimates. Because drinking during pregnancy is strongly discouraged to prevent alcohol-related problems in the fetus, women may not admit to doing so or may not admit to the actual quantities of alcohol consumed. Further, especially amongst middle class or upper class populations, children may not be screened for these disorders as they stereotypically only affect the poor. As a result, many children without obvious distinguishing facial features, particularly in the higher socioeconomic groups, may be misdiagnosed with less stigmatized conditions like attention-deficit disorder or other learning or psychiatric disorders which have similar symptoms to FASD.

How Alcohol Harms Children Before Birth

Researchers have discovered numerous mechanisms by which alcohol can interfere with the growth and development of embryos and fetuses. It can interfere with the proliferation of nerve cells, causing fewer to be produced and making some cells wind up in the wrong places. It can alter the way nerve cells develop and divide to produce new cells. It can directly kill nerve cells or derange the formation of axons, the projections that send brain messages from one cell to another. It can change the signaling pathways within cells. One reason it may be able to affect all these different processes is because it also seems to interfere with the genes that tell cells when to make proteins and when to stay silent.

Alcohol also seems to directly affect the development of two important neurotransmitter systems, the serotonin system, which appears to help regulate mood and aggression; and the glutamate system, which is involved in learning and memory. Serotonin release by cells during development seems to influence the development of receptors for this chemical messenger.

There is also a genetic component to alcohol-related birth defects. Certain genes have found to have a “protective” effect on children of drinking mothers, while others seem to predispose children to FASD if their mothers drink while pregnant. new footnote 2

Interestingly, researchers found that alcohol-related brain damage to the serotonin system could be mitigated in mice by giving the anti-anxiety drug buspirone, which affects the specific receptors that are influenced by prenatal alcohol exposure new footnote 2.

Some research has tied certain detrimental effects of alcohol to the action of genes that produce a protein called L1 adhesion factor. Children born with defects in these genes are remarkably similar to those with FASD-so researchers decided to look more closely at what L1 adhesion factor does. It appears to guide neurons to their places in the brain, making them stick together and form connections at appropriate places.

A 2003 study in the Proceedings of the National Academy of Sciences by Michael Charness and colleagues found that a protein called NAP could prevent alcohol from affecting L1 adhesion factor footnote icon. Mice given high doses of alcohol during fetal development along with NAP did not show the expected brain damage.

Alcohol-linked damage can occur at any time during pregnancy.  The specific effects seem to vary with the timing of exposure. Damage in the first trimester appears to produce facial malformations and interfere with very basic brain development. Exposure during the second trimester seems to reduce the number of brain cells, while drinking during the third trimester seems to kill off brain cells and impair the final stages of brain development that immediately precede birth.

With other toxic exposures during pregnancy, exposure later in pregnancy often causes less serious damage than exposure early on-but this does not seem to be the case with alcohol, because critical periods for brain development occur throughout pregnancy, not just at the start.

Alcohol also seems to have an overall stunting effect on growth, particularly of the head and brain. But some brain regions are especially hard-hit. For example, the corpus callosum, which connects the left and right sides of the brain, in FASD footnote icon - and approximately seven percent of people with FAS have no corpus callosum at all. This is 20 times more common than the rate of this brain defect in the general population footnote icon.

Other structures especially prone to damage are the basal ganglia, which are involved in control of movement and motivation and the cerebellum which is believed to be responsible for balance and the coordination of complex learned activities (i.e., how to ride a bike, how to play the piano, etc.). The cerebellum may also play a role in attention. The frontal lobes, which play key roles in judgment and planning also seem to be damaged by prenatal alcohol exposure.

No other recreational drug is as damaging to the developing brain; in fact, recent research suggests that much of the damage once attributed to crack cocaine in children born to mothers who smoked the drug during pregnancy was actually caused by concomitant alcohol use and other factors like stress, malnutrition and a lack of prenatal care. (This is not to suggest that cigarette smoking and cocaine use during pregnancy are safe.) new footnote 3

The Moderate Drinker

In a world of drug scare stories warning that "crack babies" were doomed to become a lost, degenerate generation, people often discount reports of harm related to psycho-active substances. Many feel that the "nanny state" is probably crying wolf again, and that just as marijuana didn't turn them into heroin addicts or crazed killers, a few drinks during pregnancy probably won't do much harm either. They figure, too, that before the discovery of FAS most women drank throughout their pregnancies and didn't produce generations of severely alcohol-damaged children.

Women who drink amounts that would define them as moderate drinkers when not pregnant-between 7-14 drinks per week- are extremely unlikely to have babies with full FAS. Nonetheless, when you compare mothers who report this level of drinking to mothers who say they didn't drink at all while expecting, studies find subtle difficulties with attention and often slightly lowered IQ's. Greater difficulty with mathematics and with memory is also reported.

A 2001 study of alcohol consumption by pregnant women found a dose/response relationship, with higher doses linked to anxious/depressed and aggressive child behavior at age 6-7 and even light alcohol consumption linked to worse behavior compared to children of nondrinkers. new footnote 3

More serious alcohol-linked deficits that can result from slightly higher levels of consumption can move children from having average intelligence to the lowest levels of the normal range, where, for example, passing math classes can become seriously problematic. Any deficit that has this result is said to cause "functional impairment." Such deficits have greater impact than those which can be discovered only by testing for subtle differences, which have hard to measure 'real world' effects.

However, some studies find no significant effects at all—for example, a 2009 study found no association between delayed acquisition of speech and low levels of drinking and only non-significant effects of binge-drinking in the second trimester new footnote 3.

There are also many factors-most of which are unknown- that can significantly modify alcohol's ability to cause functional impairments. As a result, Wayne State University Professor Sandra Jacobson estimates that only 4 in 100 children of heavy drinkers will have full FAS; another, larger group may have other FASD diagnoses but most children will not be measurably affected.

One critical determinant appears to be maternal age: in one study, a mother over thirty who drank seven or more drinks a week was 3-5 times more likely to have a child who was functionally impaired at age one in terms of motor skills and complex play than a woman that age who drank seven or fewer drinks a week footnote icon. Researchers have long known that if a woman has given birth to one FAS child, and if she drinks during her further pregnancies, each successive child will be more severely affected. Why this occurs and how age has such an effect is not known.

In the same study, children of mothers under 30 did not appear to be significantly harmed by drinking at these levels: there was no difference between the group who drank 7 to 14 drinks per week and those who drank 7 or fewer and both groups were indistinguishable from non-drinkers on measures of motor skills and complex play. On a measure of brain processing speed, however, consuming more than seven alcoholic drinks per week doubled the risk of functional impairment in all age groups.

Another key variable is drinking pattern. High concentrations of alcohol in the blood appear to do the most damage to the developing child-so "binge" drinking patterns that produce large spikes in BAC, especially if alcohol is consumed on an empty stomach, are most dangerous. In the Jacobson study, four of five women who drank at least four days a week and averaged at least five drinks per occasion had functionally impaired babies, while none of the children of the six women who drank 1.3 to 4.6 drinks per day on four or more days per week had affected children.

Genetics and stress also seem to play important roles in whether or not a woman who drinks during pregnancy will harm her child. Some studies suggest that race has genetic correlates which may predispose them to FASD susceptibility. In particular, black babies are more likely to exhibit symptoms of FASD than whites with the same amount of maternal drinking.

Chronic, unrelenting stress can also produce hormonal effects which in themselves can damage fetuses. Stress, of course, is also likely to increase the desire to drink and the amount consumed. This is one reason why there may be higher rates of FASD amongst the poor, even accounting for under-diagnosis in other groups.

Some scientists have criticized the studies on moderate drinking, saying that the research often lumps people on the heavy end of the moderate spectrum in with those who were truly light drinkers and that pregnant women who drink often say they drink less than they really do. If you separate out the truly light drinkers (two or fewer drinks per occasion, two or fewer times a week), they say, there is no effect of light drinking. But even these researchers believe that the advice to pregnant women should be to abstain entirely.

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