Fetal Alcohol Syndrome

Article Author:
Demetrios Vorgias
Article Editor:
Bettina Bernstein
Updated:
11/19/2017 8:22:54 AM
PubMed Link:
Fetal Alcohol Syndrome

Introduction

Fetal alcohol syndrome is one of a spectrum of disorders under the umbrella term of fetal alcohol spectrum disorder (FASD). There is a total of five disorders that comprise fetal alcohol spectrum disorders. They are fetal alcohol syndrome (FAS), partial fetal alcohol syndrome (pFAS), alcohol-related neurodevelopmental disorder (ARND), a neurobehavioral disorder associated with prenatal alcohol exposure (ND-PAE), and alcohol-related birth defects (ARBD). All of these fetal alcohol spectrum disorders are used to classify the wide-ranging physical and neurological effects that prenatal alcohol exposure can inflict on a fetus.

Etiology

All of the conditions that comprise fetal alcohol spectrum disorders stem from one common cause which is prenatal exposure to alcohol. Alcohol is extremely teratogenic to a fetus. Its effects are wide-ranging and irreversible. Although higher amounts of prenatal alcohol exposure have been linked to increased incidence and severity of fetal alcohol spectrum disorders, there are no studies that demonstrate a safe amount of alcohol that can be consumed during pregnancy. There is also no safe time during pregnancy in which alcohol can be consumed without risk to the fetus. Alcohol is teratogenic during all three trimesters. In summary, any amount of alcohol consumed at any point during pregnancy has the potential cause irreversible damage that can lead to a fetal alcohol spectrum disorder.

Epidemiology

Prenatal alcohol exposure is the leading cause of preventable birth defects. Because the presentation of fetal alcohol spectrum disorders can vary so widely and because of recent changes to the diagnostic criteria that define these conditions, the exact prevalence is difficult to determine. Across the United States, in the 1980s and 1990s, fetal alcohol syndrome was estimated to occur in the range of 0.5 to 2 cases per 1000 live births. However, it is widely accepted that these studies underreported the problem as the other conditions that comprise fetal alcohol spectrum disorders were not defined at the time and thus not recognized. Using the more recent definitions of fetal alcohol spectrum disorders that take into account the wide-range of effects that prenatal alcohol exposure can elicit, recent studies in the United States have shown that currently, fetal alcohol syndrome ranges from six to nine cases per 1000, and fetal alcohol spectrum disorders range from 24 to 48 cases per 1000. The higher ends of these ranges are seen in high-risk populations such as those with low socioeconomic status and those of racial and ethnic minority populations. American Indians have some of the highest rates overall. Prevalence of fetal alcohol syndrome has been reported to be as high as 1.5% among children in the foster care system.

In many cases, prenatal alcohol exposure is unintentional because women continue their normal drinking patterns before they know they are pregnant. Most women stop drinking alcohol once made aware of their pregnancy. Despite this fact, 7.6% of women report continued drinking during pregnancy.

Pathophysiology

The exact mechanism by which alcohol causes its teratogenic effects is not known. For obvious ethical reasons, formal studies on the effects of alcohol on human brain development are limited. Most of our data come from animal models and associations with alcohol exposure.

We do know that alcohol is a teratogen that causes irreversible damage to the central nervous system (CNS). From associations with alcohol exposure, we are aware that that damage is widespread, causing not only a decrease in brain volume but also damage to structures within the brain. We also know from associations that high levels of alcohol consumption in the first trimester resulted in an increased likelihood of facial and brain anomalies. High levels of alcohol consumption in the second trimester are associated with increased incidences of spontaneous abortions. Lastly, in the third trimester, high levels of alcohol consumption are associated with decreased height, weight, and brain volume. Associations with alcohol exposure show that the neurobehavioral deficits associated with fetal alcohol spectrum disorders can occur within a wide range of exposure to alcohol and at any point in the pregnancy.

From animal models, we know that prenatal alcohol exposure affects all stages of brain development through a variety of mechanism, the most significant of which result in cognitive, motor, and behavioral dysfunction.

Toxicokinetics

According to an article by Zhang et al., in the November 5, 2017 issue of Toxicology Letters, animal research that exposed the chick embryo to alcohol may help to understand the exact etiology of brain injury in fetal alcohol spectrum disorder. The cranial neural crest cells (NCCs) contribute to the formation of the craniofacial bones. Exposure to 2% ethanol (alcohol) induced craniofacial defects in the developing chick fetus. Immunofluorescent staining revealed that ethanol treatment downregulated Ap-2, Pax7 and HNK-1 expressions by cranial NCCs. The use of double-immunofluorescent stainings for Ap-2/pHIS3 and Ap-2/c-Caspase3 showed that alcohol treatment inhibited cranial NCC proliferation and increased NCC apoptosis. Alcohol exposure of the dorsal neuroepithelium increased Laminin, N-Cadherin, and Cadherin 6B expressions while Cadherin 7 expression was repressed. In situ hybridization also revealed that ethanol treatment up-regulated Cadherin 6B expression but down-regulated slug, Msx1, FoxD3 and BMP4 expressions thus affecting proliferation and apoptosis.

History and Physical

Because prenatal alcohol exposure has multiple effects on multiple organ systems, history and physical findings associated with fetal alcohol spectrum disorders vary widely. In general, diagnoses within fetal alcohol spectrum disorders have one or more of the following features: abnormal facies, central nervous system abnormalities, and growth retardation. However, the different conditions under fetal alcohol spectrum disorders have different diagnostic criteria, and some require documentation of maternal alcohol use during pregnancy.

In general, the physical findings that should raise your index of suspicion for fetal alcohol spectrum disorders are the characteristic facial features of short palpebral fissures, thin vermillion border, and a smooth philtrum. In-utero and postnatal growth retardation and microcephaly are also highly prevalent in children with prenatal alcohol exposure. Other common physical features that are associated with but not diagnostic of fetal alcohol spectrum disorders are maxillary hypoplasia, micrognathia, decreased interpupillary distance among many others. Structural defects may also occur in the cardiovascular, renal, musculoskeletal, ocular, and auditory systems.

Like the physical findings, the CNS system deficits associated with fetal alcohol spectrum disorders can vary widely. They can range from irritability, jitteriness and developmental delays in infancy, to hyperactivity, inattention, and learning disabilities in childhood that can be misdiagnosed as simple attention-deficit hyperactivity disorder (ADHD). In adolescence, the CNS abnormalities can manifest themselves in a number of ways from poor coordination, abnormal reflexes, poor academic performance, impaired problem-solving, poor social skills, deficiencies in executive functions such as cognitive planning and concept formation, poor understanding of consequences of actions, difficulties with the activities of daily living and problems with impulse control which can manifest, disrupting school, inability to maintain employment, or inappropriate sexual behavior.

The history that is associated with undiagnosed fetal alcohol spectrum disorders is fairly wide. In neonates, it is crucial to get a good prenatal history to determine prenatal alcohol exposure. For older children and young adults, the primary indicative history will be those areas pertaining to neurocognitive and behavioral impairment. Their history will point to the fact that those with fetal alcohol spectrum disorders have a high incidence of emotional and behavioral problems. Past experience with the juvenile justice system or foster care system, having a sibling with fetal alcohol spectrum disorders, recurrent unemployment, a history of substance abuse, and a history of inappropriate sexual behaviors such as improper touching and inappropriate exposure are some of the history findings that should raise the index of suspicion for fetal alcohol spectrum disorders.

Evaluation

When evaluating a patient for fetal alcohol spectrum disorders, each of the five conditions that comprise fetal alcohol spectrum disorders has its specific diagnostic criteria.

Fetal alcohol syndrome (FAS) is diagnosed by the presence of all of the following criteria: two of the three characteristic facial features (short palpebral fissures, thin vermillion border, and a smooth philtrum), growth retardation (prenatally and/or postnatally), and central nervous system defects. Because all of these criteria are met for diagnosis, fetal alcohol syndrome does not require documentation of prenatal alcohol exposure. Partial fetal alcohol syndrome (pFAS) has two of the characteristic facial features plus, depending on where alcohol exposure was documented, varies in its other criteria. Alcohol-related birth defects (ARBD) is the term used to describe those with the physical defects secondary to known fetal alcohol exposure, but who do not have neurobehavioral deficits. On the opposite end of the spectrum, alcohol-related neurodevelopmental disorder (ARND) describes those with neurobehavioral impairment in the setting of documented prenatal alcohol exposure but have minimal to no physical findings and cannot be diagnosed before three years of age. Neurobehavioral disorder associated with prenatal alcohol exposure (ND-PAE) is very similar to alcohol-related congenital disabilities but may involve some physical features.

Because of the wide-ranging presentation and large overlap with other genetic and environmental etiologies such as illicit drug and tobacco use, a primary care provider cannot make a definitive diagnosis of fetal alcohol spectrum disorders. Once a primary care provider has a strong suspicion for fetal alcohol spectrum disorders, their patient should be referred to a team of specialists to rule out other possible conditions and make a definitive diagnosis.

The composition diagnostic team varies based on the age of the patient. In general, the diagnostic team includes a pediatrician and/or hysician who may have expertise in fetal alcohol spectrum disorders, an occupational therapist, speech language pathologist, and psychologist.

Treatment / Management

Given that the CNS damage from prenatal alcohol exposure is permanent, there is no cure for fetal alcohol spectrum disorders. However, treatment to mitigate the effects of fetal alcohol spectrum disorders is available. Given the extensive variation in presentation and damage that prenatal exposure to alcohol can cause, treatment for fetal alcohol spectrum disorders is often tailored and specific to individuals. One of the most common treatment approaches is using the medical home to coordinate developmental and educational resources. This treatment modality takes into account the fact that fetal alcohol spectrum disorders disrupt normal neurobehavioral development and that each person can have different manifestations of those disruptions. This treatment methodology seeks to tailor specific therapies to reinforce and address any delays or deficiencies with additional education, practice, and reminders. In summary, when it comes to fetal alcohol spectrum disorders, as is true of most conditions in medicine, the best treatment is prevention.

Prognosis

Prognosis is guarded; however, recent research with chick embryos may help guide future treatments to reverse the damage caused to the brain by prenatal alcohol exposure.