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Questions and Answers

What percentage of birth defects have a clear etiology?

70 percent

80 percent

50 percent

20 percent (correct)

What is the definition of teratology?

Study of maternal health during pregnancy

Study of birth defects and their etiology (correct)

Study of pregnancy complications

Study of normal fetal development

Which of the following best describes a teratogen?

An agent that enhances fetal growth

An agent that causes permanent structural abnormalities (correct)

An agent that has no impact on fetal development

An agent affecting organ maturation and function

What is the approximate percentage of newborns with a major congenital abnormality detectable at birth?

2 to 3 percent Signup and view all the answers

What function does a hadegen interfere with during development?

Organ maturation and function Signup and view all the answers

Which FDA pregnancy category indicates that well-controlled studies in humans show no risk to the fetus?

Category A Signup and view all the answers

What does Category C imply regarding the effects of medication on the fetus?

Adverse effects observed in animal studies with no well-controlled human studies Signup and view all the answers

Which category indicates evidence of risk to the human fetus?

Category D Signup and view all the answers

What does Category X signify in relation to medication exposure during pregnancy?

Fetal abnormalities demonstrated in well-controlled studies Signup and view all the answers

What is represented by Category B in the FDA classifications?

Animal studies show no risk; no well-controlled human studies conducted Signup and view all the answers

What is considered the leading cause of preventable developmental disabilities worldwide?

Fetal alcohol spectrum disorder Signup and view all the answers

Which medication is linked to the highest risk of anomalies such as orofacial clefts and cardiac malformations?

Valproic acid Signup and view all the answers

What describes the effects of ACE inhibitors during pregnancy?

Fetal hypotension and renal hypoperfusion Signup and view all the answers

What is a major characteristic of Fetal Alcohol Syndrome?

Short palpebral fissures Signup and view all the answers

Which newer antiepileptic medications do not appear to pose risks similar to older agents like valproic acid?

Levetiracetam and lamotrigine Signup and view all the answers

What may result from oligohydramnios during pregnancy?

Pulmonary hypoplasia Signup and view all the answers

What pattern of congenital malformations is associated with high-dose Fluconazole during the first trimester?

Antley-Bixler syndrome Signup and view all the answers

What is a significant risk associated with prenatal lead exposure?

Fetal growth abnormalities Signup and view all the answers

Which medication is categorized as a Category X drug due to its potential severe effects on fetal development?

Radioiodine-131 Signup and view all the answers

What type of malformation is specifically associated with thalidomide exposure during early pregnancy?

Phocomelia Signup and view all the answers

What potential harm does prenatal mercury exposure cause?

Cognitive impairment Signup and view all the answers

At what stage of pregnancy can radioactive iodine-131 begin to accumulate in the fetal thyroid gland?

12 weeks gestation Signup and view all the answers

What serious condition can arise in pre-term newborns due to the use of chloramphenicol?

Gray baby syndrome Signup and view all the answers

Which of the following antibiotics is associated with nephrotoxicity and ototoxicity?

Gentamicin Signup and view all the answers

What potential adverse effect can sulfonamides cause if administered close to preterm delivery?

Worsening of neonatal hyperbilirubinemia Signup and view all the answers

What is a notable side effect of tetracycline in children?

Tooth discoloration Signup and view all the answers

What harmful compounds are found in cigarette smoke that can affect fetal development?

Nicotine and carbon monoxide Signup and view all the answers

What congenital malformation is associated with the use of Methotrexate during pregnancy?

Craniosynostosis Signup and view all the answers

What condition may result from fetal exposure to Diethylstilbestrol?

Hypospadias Signup and view all the answers

Which teratogenic effect is associated with Mycophenolate Mofetil?

Cardiac defects Signup and view all the answers

What specific cardiac condition is linked to Lithium exposure during pregnancy?

Ebstein anomaly Signup and view all the answers

Which of the following effects is NOT associated with prenatal exposure to Amphetamines?

Congenital heart defects Signup and view all the answers

What is a potential consequence of exposure to Retinoids during pregnancy?

Neural crest defects Signup and view all the answers

What anomalies may result from fetal exposure to Testosterone and anabolic steroids?

Ambiguous genitalia Signup and view all the answers

What oral malformation is commonly associated with Cocaine use during pregnancy?

Cleft palate Signup and view all the answers

Study Notes

Congenital Defects in Pregnancy

Approximately 80% of birth defects lack a clear cause, highlighting the complexity of congenital anomalies.
Around 15% of congenital defects are attributed to chromosomal or genetic factors, indicating a significant genetic influence.
Major congenital abnormalities are detected at birth in 2 to 3% of all newborns, emphasizing the importance of prenatal screenings.

Teratology

Teratology is the scientific study of birth defects and their causes, derived from the Greek word "teratos," meaning monster.
A teratogen is any agent that can cause permanent changes in form or function during the embryonic or fetal development stages.
Teratogens primarily result in structural abnormalities in the developing fetus.
Hadegens are agents that disrupt the normal maturation and functioning of organs during development.
Trophogens are agents that influence growth patterns in the developing fetus, affecting overall growth.

Criteria for Determining Teratogenicity

Essential criteria include thorough case investigations, especially for specific defects or syndromes.
Proof of exposure during critical periods of development is vital for establishing teratogenic effects.
Epidemiological studies should demonstrate consistent findings with:
- Exclusion of bias to ensure reliability.
- Adjustment for confounding variables to clarify true associations.
- Adequate sample size to ensure statistical power for detecting differences.
- Preferably prospective ascertainment for accurate data collection.
- A relative risk (RR) of 3.0 or greater is required; some experts recommend an RR of 6.0 or higher.
In cases of rare environmental exposures linked to rare defects, documentation of at least three reported cases is necessary; this is particularly relevant for severe defects.

Ancillary Criteria

The biological plausibility of the association should be established to support the link between exposure and teratogenicity.
Evidence of teratogenicity in animal studies is significant but not a strict requirement.
The teratogenic agent must act in an unaltered form within experimental models to reinforce findings.

FDA Drug Categories for Pregnancy Risk

Category A: Safe for use during pregnancy; well-controlled human studies confirm no risk to the fetus.
Category B: No risk found in animal studies; however, no well-controlled studies in humans are available.
Category C: Adverse effects observed in animal studies; no well-controlled human studies conducted, indicating potential risks.
Category D: Confirmed evidence of risk to the human fetus based on available data.
Category X: Well-controlled studies in animals or humans show significant fetal abnormalities; contraindicated in pregnancy.

Alcohol (Ethanol)

Ethanol is a significant teratogen and the primary cause of preventable developmental disabilities globally.
Fetal Alcohol Spectrum Disorder (FASD) encompasses a range of effects caused by alcohol exposure during pregnancy.
Fetal Alcohol Syndrome (FAS) is characterized by:
- Short palpebral fissures
- Epicanthal folds
- Flat midface
- Hypoplastic philtrum
- Thin upper vermilion border

Antiepileptic Medications

Most commonly linked anomalies include orofacial clefts, cardiac malformations, and neural-tube defects.
Valproic acid is associated with the highest risk for these anomalies.
Fetal Hydantoin Syndrome is a specific condition resulting from exposure to certain antiepileptic medications.
Newer antiepileptic drugs, such as levetiracetam and lamotrigine, do not demonstrate the same risk levels.

Angiotensin-Converting Enzyme Inhibitors and Angiotensin-Receptor Blockers

ACE inhibitors can lead to ACE-inhibitor fetopathy, affecting fetal development.
Normal renal development in the fetus is dependent on the renin-angiotensin system.
Fetal exposure can result in:
- Hypotension and renal hypoperfusion
- Ischemia and anuria
- Fetuses may experience growth restriction and calvarium maldevelopment.
Oligohydramnios can occur, leading to complications such as pulmonary hypoplasia and limb contractures.
Maternal pre-pregnancy intake of these medications does not adversely affect the baby.

Fluconazole

Associated with congenital malformations resembling Antley-Bixler syndrome.
Risk primarily linked to chronic, high-dose treatment (400-800 mg daily) during the first trimester.
Low-dose Fluconazole is not recommended for use.

Radioiodine

Classified as Category X with significant risks during pregnancy.
Radioactive iodine-131 is utilized for treating thyroid cancer and thyrotoxicosis, as well as for diagnostic scanning.
Crosses the placenta and accumulates in the fetal thyroid gland by 12 weeks gestation.
Can lead to severe or irreversible fetal and neonatal hypothyroidism.
Pregnancy testing is essential prior to administering radioiodine-131.

Lead Exposure

Prenatal lead exposure is linked to fetal growth abnormalities.
Associated with childhood developmental delays and behavioral issues.

Mercury Exposure

Prenatal mercury exposure disrupts neuronal cell division and migration.
Can result in developmental delays, microcephaly, and severe brain damage.

Thalidomide and Lenalidomide

Known as severe human teratogens with high risk of malformations.
Exposure during 34 to 50 days of menstrual age causes malformations in approximately 20% of fetuses.
Characteristic malformation includes phocomelia, characterized by the absence of one or more long bones.
About 40% of affected newborns do not survive their neonatal period.

Tobacco

Cigarette smoke contains a complex mix of substances including nicotine, cotinine, cyanide, thiocyanate, carbon monoxide, cadmium, lead, and various hydrocarbons.
It has vasoactive effects that can reduce oxygen levels in the body.

Antimicrobials

Chloramphenicol:
- Not teratogenic but can cause gray baby syndrome in pre-term newborns.
- Newborns struggle to conjugate and excrete the drug, leading to symptoms like abdominal distention, respiratory issues, ashen-gray color, and vascular collapse.
Gentamicin or Streptomycin:
- Associated with nephrotoxicity (kidney damage) and ototoxicity (hearing impairment).
Sulfonamides:
- Administering near the time of preterm delivery may exacerbate neonatal hyperbilirubinemia (high bilirubin levels).
Tetracycline:
- Known to cause tooth discoloration, particularly in developing dentition.

Antineoplastic Agents

Methotrexate: Associated with fetal growth restriction and several craniofacial deformities including clover-leaf skull, hypoplastic supraorbital ridges, and wide nasal bridge.
Impacts on the ears include small posteriorly rotated ears and low-set ears, while also potentially causing micrognathia and limb abnormalities.

Sex Hormones

Testosterone and Anabolic Steroids: Exposure in female fetuses can lead to varying levels of virilization, potentially resulting in ambiguous genitalia, similar to congenital adrenal hyperplasia.
Diethylstilbestrol (DES): Female exposure may cause a hypoplastic, T-shaped uterine cavity and abnormalities in the cervical region. In males, may lead to epididymal cysts, microphallus, hypospadias, cryptorchidism, and testicular hypoplasia.

Immunosuppressants

Corticosteroids: Linked to the development of cleft lip and palate.
Mycophenolate Mofetil: Noted as a potent teratogen associated with microtia, auditory canal atresia, and multiple anomalies like clefts and coloboma. It may lead to short fingers with hypoplastic nails and various cardiac defects.

Psychiatric Medications

Lithium: Associated with Ebstein anomaly, a rare cardiac defect, and can lead to neonatal lithium toxicity with potential arrhythmias, hypoglycemia, nephrogenic diabetes insipidus, and floppy infant syndrome.
Retinoids: Vitamin A derivatives recognized as potent teratogens that may inhibit neural-crest cell migration during embryogenesis, leading to craniofacial defects known as retinoic acid embryopathy.

Recreational Drugs

Amphetamines: Linked to hypertensive complications, placental abruption, preterm birth, and increased stillbirth rates. Also associated with behavioral abnormalities in offspring.
Cocaine: Known to cause cleft palate, cardiovascular issues, urinary tract anomalies, fetal growth restriction, and preterm delivery. Linked to heightened risks of behavioral abnormalities and cognitive impairments in children.

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Description

This quiz covers essential concepts related to congenital defects and teratology, including the etiology of birth defects and the role of teratogens during embryonic and fetal development. Explore the statistics surrounding birth defects and their genetic origins. Test your understanding of these critical topics in prenatal health.