diease

Fetal Alcohol Syndrome


Fetal Alcohol Syndrome overview and Definition

Fetal alcohol syndrome occurs when the mother consumes alcohol during the pregnancy and it causes severe complications.


Pathophysiology

The alcohol crosses the placental barrier rapidly and it reaches the fetus. The studies reveals equivalent fetal and maternal alcohol concentrations, suggesting an umimpeded bidirectional movement of alcohol between the two 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 alcohol reaches the fetus by crossing the placenta. Ethanol and its metabolites acetaldehyde can alter fetal development by disrupting cellular differentiation and growth, disrupting DNA and protein synthesis and inhibits the cell migration. Both the ethanol and acetaldehyde modifies the intermediary metabolism of carbohydrates, proteins and fats.  They also deteriorates the transfer of aminiacids, glucose, folic acid, zinc and other nutrients, across the placental barrier and it also indirectly affects the fetal growth due to intrauterine nutrient deprivation.

High  levels of erythropoietin in the umbilical cord blood of newborns exposed to alcohol are reported and suggest a state of chronic fetal hypoxia.

Studies suggest 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.

 


Routes of Transmission

The main route of transmission is by vertical transmission that is by the transmission from the mother to the foetus.


Clinical signs & symptoms

A person with an FASD might have:

  • Low body weight
  • Poor coordination
  • Hyperactive behavior
  • Difficulty with attention
  • Poor memory
  • Difficulty in school (especially with math)
  • Learning disabilities
  • Speech and language delays
  • Intellectual disability or low IQ
  • Poor reasoning and judgment skills
  • Sleep and sucking problems as a baby
  • Vision or hearing problems
  • Problems with the heart, kidneys, or bones
  • Shorter-than-average height
  • Small head size
  • Abnormal facial features, such as a smooth ridge between the nose and upper lip (this ridge is called the philtrum)


Differential Diagnosis

In patients with suspected fetal alcohol syndrome (FAS), consider chromosomal analysis to rule out unbalanced translocations or visible deletions. Also consider fluorescent in-situ hybridization (FISH) of 22q11 region to rule out deletion.

Optical coherence tomography:

This is the preliminary screening tool for phenotyping and quantifying congenital heart defects associated with prenatal alcohol exposure.

Diffusion tensor imaging:

It reveals the effects of prenatal alcohol exposure on the brain structure of newborns. It also used to analyse the white matter development in newborns whose mother has drank alcohol during the pregnancy. The white matter defects reveals the abnormalities in the infants’s brain.


Prognosis

The child may have 90% chances for improper brain function


Prevention

The mother should restrain from alcohol when she is pregnant.


Reference

https://www.mayoclinic.org/diseases-conditions/fetal-alcohol-syndrome/symptoms-causes/

https://emedicine.medscape.com/article/974016-overview

https://www.cdc.gov/ncbddd/fasd/facts.html

https://www.ncbi.nlm.nih.gov/books/NBK448178/