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Chapter 6

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PSYC 3850
Carol Anne Hendry

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 21 pair in Group G becomes attached to chromosome of 15 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 38 week of gestation generally classified as preterm; 38-4week are term; after 42dweek are postterm nd o BW is 2 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, enlargement of the heart, liver and spleen, and deterioration of body tissues. Most cases fetus dies in late 2 /early 3 trimester and is stillborn. Moderate form known as icterus gravis occurs more frequently because infant’s delivery induced before term to prevent progression of disease  High level of bilirubin (from metabolism of red blood cells) accounts for jaundice and any central nervous system damage, as bilirubin level rises, adequate excretion cannot occur and molecules enter skin tissue with toxic effect (kernicterus). If infant survives the first week, outlook for survival is good  Possibility of impact on neurological system depends on severity of hyperbilirubinemia and accompanying illnesses occurring during neonatal period - Trauma During Early Pregnancy o Drug or chemical ingestion and maternal infection  Teratogenic effects of exposures poorly understood, but timing of exposure probably leads to specific kinds of anomalies st  When mother contracts rubella in 1 trimester, resulting anomalies probably related to timing of fetal exposure rather than specific effects of virus  Effects on fetus include intrauterine growth retardation, central nervous sys
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