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Questions and Answers
What is a common characteristic of Trisomy 13?
What is a common characteristic of Trisomy 13?
Which of the following statements is true regarding Klinefelter syndrome?
Which of the following statements is true regarding Klinefelter syndrome?
Which feature is not typically associated with Turner syndrome?
Which feature is not typically associated with Turner syndrome?
What is the estimated incidence of Klinefelter syndrome in males?
What is the estimated incidence of Klinefelter syndrome in males?
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Structural abnormalities of chromosomes are generally a result of what?
Structural abnormalities of chromosomes are generally a result of what?
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What percentage of individuals with Down syndrome have Trisomy 21?
What percentage of individuals with Down syndrome have Trisomy 21?
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At what maternal age does the risk of having a child with Down syndrome increase to one in 300?
At what maternal age does the risk of having a child with Down syndrome increase to one in 300?
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Which feature is NOT commonly associated with Down syndrome?
Which feature is NOT commonly associated with Down syndrome?
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Which of the following conditions is associated with a higher incidence in individuals with Down syndrome?
Which of the following conditions is associated with a higher incidence in individuals with Down syndrome?
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What distinguishes Mosaic Down syndrome from other types?
What distinguishes Mosaic Down syndrome from other types?
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What is the risk of having a child with Down syndrome at age 40?
What is the risk of having a child with Down syndrome at age 40?
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What is a typical consequence of Trisomy 18?
What is a typical consequence of Trisomy 18?
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Which of the following is a physical characteristic of Down syndrome?
Which of the following is a physical characteristic of Down syndrome?
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What percentage of babies are born with some type of birth defect?
What percentage of babies are born with some type of birth defect?
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Which factor is NOT commonly associated with the occurrence of birth defects?
Which factor is NOT commonly associated with the occurrence of birth defects?
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What term is used to describe factors or agents that cause birth defects?
What term is used to describe factors or agents that cause birth defects?
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Which of the following congenital malformations is NOT associated with the Rubella virus?
Which of the following congenital malformations is NOT associated with the Rubella virus?
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Which of the following is a consequence of maternal consumption of alcohol during pregnancy?
Which of the following is a consequence of maternal consumption of alcohol during pregnancy?
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Which of the following lifestyle choices increases the risk of delivering a baby with birth defects?
Which of the following lifestyle choices increases the risk of delivering a baby with birth defects?
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What is defined as a structural defect that involves a body part being malformed or missing?
What is defined as a structural defect that involves a body part being malformed or missing?
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Which teratogen is associated with limb defects, heart malformations, and other serious conditions?
Which teratogen is associated with limb defects, heart malformations, and other serious conditions?
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Which of the following factors may contribute to birth defects due to its effect during the first three months of pregnancy?
Which of the following factors may contribute to birth defects due to its effect during the first three months of pregnancy?
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How many newborns die each year worldwide due to birth defects?
How many newborns die each year worldwide due to birth defects?
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Which of the following is a common structural defect?
Which of the following is a common structural defect?
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What is the purpose of prenatal ultrasounds in the context of birth defects?
What is the purpose of prenatal ultrasounds in the context of birth defects?
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Which statement about Down syndrome is accurate?
Which statement about Down syndrome is accurate?
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What is one method of preventing neural tube defects?
What is one method of preventing neural tube defects?
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Which factor may increase the risks associated with pregnancy and birth defects?
Which factor may increase the risks associated with pregnancy and birth defects?
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Which of the following is NOT a recommended method to reduce the incidence of birth defects?
Which of the following is NOT a recommended method to reduce the incidence of birth defects?
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What is the significance of a blood test known as the newborn screen?
What is the significance of a blood test known as the newborn screen?
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What should physicians consider when prescribing drugs to women of childbearing age?
What should physicians consider when prescribing drugs to women of childbearing age?
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What is the primary cause of Cri-du-chat syndrome?
What is the primary cause of Cri-du-chat syndrome?
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Which of the following best describes Angelman syndrome?
Which of the following best describes Angelman syndrome?
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Which statement about spina bifida is accurate?
Which statement about spina bifida is accurate?
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What is a common outcome of microdeletion on paternal chromosome 15?
What is a common outcome of microdeletion on paternal chromosome 15?
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What main developmental issues might children with Miller-Dieker syndrome face?
What main developmental issues might children with Miller-Dieker syndrome face?
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What is the most serious type of spina bifida?
What is the most serious type of spina bifida?
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Which factor does NOT contribute to neural tube defects (NTDs)?
Which factor does NOT contribute to neural tube defects (NTDs)?
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Individuals with Prader-Willi syndrome often present with which of these characteristics?
Individuals with Prader-Willi syndrome often present with which of these characteristics?
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Study Notes
Birth Defects
- 3-4% of babies are born with a birth defect, globally affecting 1 in every 33 babies
- Birth defects can be mild or severe, with some being life-threatening
- An estimated 303,000 newborns die annually due to birth defects within 4 weeks of birth
Causes of Birth Defects
- Genetics, lifestyle choices, exposures to certain medications and chemicals, infections during pregnancy, and a combination of these factors can contribute to birth defects
Risk Factors of Birth Defects
- All pregnant women are at risk of delivering a child with a birth defect
- Risk factors include:
- Family history of birth defects or genetic disorders
- Drug use, alcohol consumption, or smoking during pregnancy
- Maternal age of 35 years or older
- Inadequate prenatal care
- Untreated viral or bacterial infections
- Certain high-risk medications (e.g., isotretinoin, lithium)
- Existing medical conditions in the mother (e.g., diabetes)
Teratogens Associated With Human Malformations
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Infectious agents:
- Rubella: cataracts, glaucoma, heart defects, deafness, tooth abnormalities
- Cytomegalovirus: microcephaly, blindness, intellectual disability, fetal death
- Herpes simplex virus: microphthalmia, microcephaly, retinal dysplasia
- Varicella: limb hypoplasia, intellectual disability, muscle atrophy
- HIV: microcephaly, growth retardation
- Toxoplasmosis: hydrocephalus, cerebral calcifications, microphthalmia
- Syphilis: intellectual disability, deafness
-
Physical agents:
- X-rays: microcephaly, spina bifida, cleft palate, limb defects
- Hyperthermia: anencephaly, spina bifida, intellectual disability, facial defects, cardiac abnormalities, omphalocele, limb defects
-
Chemical agents:
- Cocaine: growth retardation, microcephaly, behavioral abnormalities, gastroschisis
- Alcohol: fetal alcohol syndrome, short palpebral fissures, maxillary hypoplasia, heart defects, intellectual disability
- Thalidomide: limb defects, heart malformations
- Aminopterin: anencephaly, hydrocephalus, cleft lip and palate
Common Birth Defects
-
Structural defects (missing or malformed body part):
- Heart defects
- Cleft lip or palate
- Spina bifida
- Clubfoot
-
Functional or developmental birth defects (body part or system not working properly):
- Down syndrome
- Sickle cell disease
Diagnosis of Birth Defects
- Prenatal ultrasounds can diagnose certain birth defects in utero
- More in-depth screening options (e.g., blood tests, amniocentesis) are available for higher-risk pregnancies
- Prenatal tests can identify maternal infections or conditions harmful to the baby
- Physical examinations and hearing tests are used after birth
- Newborn screen blood tests can diagnose some defects shortly after birth before symptoms appear
Prevention of Birth Defects
- Many birth defects are preventable
- Supplementation with iodine prevents mental retardation and bone deformities from cretinism
- Strict metabolic control in women with diabetes or phenylketonuria before conception reduces defects
- Folate supplementation lowers neural tube defects (spina bifida, anencephaly) and hyperthermia-related abnormalities
- Avoiding alcohol and drugs during pregnancy reduces defects
- Physicians should consider pregnancy and potential teratogenicity when prescribing drugs to women of childbearing age
- Retinoids (acne treatment) can cause craniofacial, cardiac, and neural tube defects
Down Syndrome (Trisomy 21)
- Characterized by an extra copy of chromosome 21, leading to changes in body and brain development
- Incidence: 1 in 2,000 conceptuses for women under 25, increasing with maternal age (1 in 300 at age 35, 1 in 100 at age 40)
- Individuals with Down syndrome typically have growth retardation, varying degrees of intellectual disability, craniofacial abnormalities
- Higher incidence of leukemia, infections, thyroid dysfunction, and premature aging
- Nearly all develop Alzheimer's disease after age 35
Common Physical Features of Down Syndrome
- Flattened face, especially the bridge of the nose
- Almond-shaped eyes that slant up
- Short neck
- Small ears
- Tongue sticking out of the mouth
- Tiny white spots on the iris
- Small hands and feet
- Single line across palm of hand (palmar crease)
- Small pinky fingers curved towards the thumb
- Poor muscle tone or loose joints
- Shorter height in childhood and adulthood
Types of Down Syndrome
- Trisomy 21: 95% of cases, with three copies of chromosome 21 in each cell
- Translocation Down syndrome: 3% of cases, extra chromosome 21 attached to a different chromosome
- Mosaic Down syndrome: 2% of cases, some cells have three copies of chromosome 21, others have two
Trisomy 18 and Trisomy 13
-
Trisomy 18:
- Features: intellectual disability, congenital heart defects, low-set ears, finger/hand flexion, deficient mandible, renal anomalies, syndactyly, skeletal malformations
- Incidence: 1 in 5,000 newborns
- 85% lost during pregnancy, those born alive usually die by 2 months
-
Trisomy 13:
- Features: intellectual disability, holoprosencephaly, congenital heart defects, deafness, cleft lip and palate, eye defects
- Incidence: 1 in 20,000 live births, 90% die within the first month
Klinefelter Syndrome
- Extra copy of the X chromosome in males
- Incidence: 1 in 500 males
- Often not diagnosed until adulthood
- Affects testicular growth, leading to reduced testosterone production
- Can cause reduced muscle mass, body and facial hair, and enlarged breast tissue
- Most men with Klinefelter syndrome produce little or no sperm
Turner Syndrome (Monosomy X)
- Missing or partially missing X chromosome in females
- Incidence: 1 in 2,000 female live births
- Absence of ovaries (gonadal dysgenesis) and short stature
- Other features: webbed neck, lymphedema, skeletal deformities, low-set ears, broad chest with widely spaced nipples
Birth Defects Due to Structural Abnormalities of Chromosomes
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Involve one or more chromosomes, usually caused by chromosome breakage
-
Breakage caused by environmental factors (e.g., viruses, radiation, drugs)
-
Cri-du-chat syndrome:
- Partial deletion of short arm of chromosome 5
- Cat-like cry, microcephaly, intellectual disability, congenital heart disease
-
Microdeletions of few genes:
- Angelman syndrome: microdeletion in maternal chromosome 15, intellectual disability, speech problems, motor development issues, laughter
- Prader-Willi syndrome: microdeletion in paternal chromosome 15, hypotonia, obesity, intellectual disability, hypogonadism, cryptorchidism
- Miller-Dieker syndrome: microdeletion in both parents' chromosome 17, developmental delay, seizures, cardiac and facial abnormalities
Neural Tube Defects (NTD)
- Occur when the neural tube does not close properly during pregnancy
- Forms the brain and spinal cord
- Most common NTDs: spina bifida (spinal cord defect) and anencephaly (brain defect)
Spina Bifida
- Neural tube defect where the backbone does not close completely, damaging the spinal cord and nerves
- Severity ranges from mild to severe based on the size and location of the opening and the extent of damage to the spinal cord and nerves
Types of Spina Bifida
- Myelomeningocele: most serious, sac of fluid with spinal cord and nerves protruding through the opening in the back, causing damage
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Description
This quiz explores the critical information regarding birth defects, including their prevalence, causes, and risk factors. Understand the genetic, lifestyle, and environmental influences that impact fetal development and learn about the precautions pregnant women can take. It's essential for anyone looking to deepen their knowledge about maternal and infant health.
