PSYC 3850 Chapter Notes - Chapter 6: Intrauterine Growth Restriction, Intellectual Disability, Hemolytic Disease Of The Newborn

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Chapter 6: Early Influences and Causation
Early Causation; The Fetus and Infant at Risk
Genetic Causation
- Chromosomal Aberration
o Occur when some abnormality emerges in number or configuration of chromosomes in the body
o New kind of abnormal condition involves extra chromosomes, such as 3 chromosomes in position 21 or 2 or more X- or
Y-chromosomes. This can also involve abnormally shaped chromosomes
o Turner Syndrome (gonadal aplasia) when 45 chromosomes present with only single X-chromosome
Nearly always female
o Number of abnormalities occur on chromosomes of Groups A through G, these chromosomes referred to as autosomal
because they contain genetic material that does not involve sex characteristics
o Down Syndrome can occur from any 1 of 3 different aberrations of autosomal chromosomes
Characteristics lateral upward slope of eyes, protruding tongue, short nose, flattened head, short, stocky
build
Trisomy extra chromosome occurs in Group G, most common and has definite correlation with maternal age
Translocation occurs in 8% affected infants born to mothers < 30 and 2% in mothers > 30. Some of
chromosomal material of 21st pair in Group G becomes attached to chromosome of 15th pair in Group D,
causing extra long chromosome
Parent can either be carrier or can occur by chance chromosomal error
Mosaicism cells of individual’s body identified as mixed, error occurs during very early cell divisions after
fertilization.
- Genetic Errors
o Conditions resulting from inheritance factors involving specific genes
o Prader-Willi syndrome - 1/15,000 births, results in mild to moderate intellectual disabilities
o Phenylketonuria (PKU) transmitted by autosomal recessive gene. Produce les of enzyme necessary for metabolism
phenylalanine
Prenatal Causation
- Birth Weight (BW) and Gestational Age (GA)
o Babies delivered before 38th week of gestation generally classified as preterm; 38-42nd week are term; after 42nd week
are postterm
o BW is 2nd important factor in infant mortality and neurodevelopmental deficits
o “Small…”, “appropriate…” or “large for GA
- Predisposing Factors
o Mother’s age and pregnancy history significant factors in risks to fetus; mothers < 20 or > 35 more likely to suffer early
pregnancy termination than those between ages of 20-35
o Socioecononmic factors also related
o Mothers who have had multiple pregnancies account for high % of infants born with low GA and BW mainly
difficulties of placental problems that lead to ineffective transfer of nutrients across placenta late in pregnancy
Labor and delivery usually preterm and infant usually small for GA
o Maternal smoking infant growth retarded substantially; mothers tend to eat less and vascular constriction caused by
smoking restricts uterine blood flow
o Fetal Alcohol Syndrome facial abnormalities, cardiac defects, cognitive deficits, neurological abnormalities, autism,
behavioural deficits and intellectual disabilities even moderate alcohol consumption can result in fetal problems
o Neurological development crucial to health and well-being of infant
o Maternal nutrition important to fetal health
- Associated Problems
o Respiratory and Cardiac difficulties lead to serious interference with delivery of oxygen to developing fetal tissues
o Infection infants have few physiological mechanisms to fight infections, can progress rapidly to serious illness like
pneumonia or meningitis
Infection of central nervous system (CNS) leads to grave and permanent consequences, affecting child’s
neurological capacity in later life
o Nutrition and Oxygen Intake Supply of glucose, proteins and oxygen through placenta important in last few months of
gestation nourish all growing tissues, needed for survival, can lead to many complications
- Influences from Maternal-Fetal Interaction
o Infants of diabetic mothers high risk because of excessive BW for GA, but usually low GA prone to several serious
illnesses during neonatal period (lung disorders, seizures, hypoglycemia, etc.), severity of maternal diabetes largely
influences neurological impact on infant
o Problem of maternal-fetal Rh factor incompatibility has more direct effect on infant’s neurological capacity
Mother has negative Rh blood factor and infant has positive Rh factor, mother reacts to infant’s positive factor
by developing antibodies that destroy infant’s blood cells
Infant’s condition called erythroblastosis fetalis; the higher the level of antibodies in the mother’s blood, the
more serious the effect on the fetus. In most severe form (fetal hydrops), fetus develops severe anemia,
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Document Summary

Early causation; the fetus and infant at risk. Chromosomal aberration: occur when some abnormality emerges in number or configuration of chromosomes in the body, new kind of abnormal condition involves extra chromosomes, such as 3 chromosomes in position 21 or 2 or more x- or. This can also involve abnormally shaped chromosomes: turner syndrome (gonadal aplasia) when 45 chromosomes present with only single x-chromosome. Characteristics lateral upward slope of eyes, protruding tongue, short nose, flattened head, short, stocky build. Trisomy extra chromosome occurs in group g, most common and has definite correlation with maternal age. Translocation occurs in 8% affected infants born to mothers < 30 and 2% in mothers > 30. Some of chromosomal material of 21st pair in group g becomes attached to chromosome of 15th pair in group d, causing extra long chromosome. Parent can either be carrier or can occur by chance chromosomal error.

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