Prenatal Diagnosis and Ultrasound Examination

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Questions and Answers

What is the primary purpose of using ultrasound during prenatal diagnosis?

To determine the gender of the fetus

To detect malformations and assess fetal growth (correct)

To measure the mother's blood pressure

To analyze maternal diet

Which congenital malformations can be detected by ultrasound?

Heart defects and facial abnormalities (correct)

Only external limb defects

All genetic disorders

Neurological disorders only

What does an increase in maternal serum α-fetoprotein (AFP) typically indicate?

Normal fetal development

Down syndrome

Potential neural tube defects or other abnormalities (correct)

Fetal gender identification

Which technique provides higher resolution images during ultrasound examinations?

Transvaginal ultrasound (D) Signup and view all the answers

What factors are evaluated using ultrasound in a prenatal setting?

Fetal age, congenital anomalies, and uterine environment (C) Signup and view all the answers

When do α-fetoprotein (AFP) levels peak during pregnancy?

Approximately 14 weeks of gestation (D) Signup and view all the answers

What is the significance of decreasing AFP levels in maternal serum?

Indicates potential fetal abnormalities like Down syndrome (B) Signup and view all the answers

Which of the following is NOT typically a benefit of prenatal diagnosis?

Improving maternal dietary habits (A) Signup and view all the answers

What is considered prepregnancy obesity based on BMI?

BMI >30 kg/m2 (C) Signup and view all the answers

What condition is NOT associated with prepregnancy obesity?

Cystic fibrosis (A) Signup and view all the answers

What potential effect does hypoxia have on pregnancy outcomes?

Induces congenital malformation (A) Signup and view all the answers

Which metal exposure has been linked to increased risks of neurological disorders in pregnancy?

Lead (B) Signup and view all the answers

Which of the following factors is linked to an increased risk of birth defects in offspring?

Advanced paternal age (C) Signup and view all the answers

What does male-mediated teratogenesis primarily involve?

Mutations in male germ cells (C) Signup and view all the answers

How does maternal hypoxia affect the size of infants born at high altitudes?

Decreases their size (C) Signup and view all the answers

Which of the following is true about paternal smoking and birth defects?

It is linked to low birth weight. (D) Signup and view all the answers

What percentage of liveborn infants is affected by major structural anomalies?

2% to 3% (B) Signup and view all the answers

Which factor accounts for the largest percentage of birth defects?

Unknown causes (A) Signup and view all the answers

What is the leading cause of infant mortality?

Birth defects (D) Signup and view all the answers

Which of the following terms refers to the study of structural anomalies present at birth?

Teratology (A) Signup and view all the answers

What is the likelihood of having a major malformation for infants with two minor anomalies?

10% (C) Signup and view all the answers

During which weeks of gestation do most malformations originate?

Third to eighth (A) Signup and view all the answers

Which of the following describes deformations in the context of birth defects?

Result from mechanical forces (D) Signup and view all the answers

What is a common indicator of underlying serious defects in infants?

Minor anomalies (C) Signup and view all the answers

What abnormality was most directly linked to thalidomide use during pregnancy?

Meromelia (A) Signup and view all the answers

Which of the following teratogenic agents is specifically associated with causing deafness?

Streptomycin (B) Signup and view all the answers

What condition is alcohol consumption during pregnancy primarily associated with?

Fetal alcohol syndrome (A) Signup and view all the answers

What is the primary risk of using ACE inhibitors during pregnancy?

Renal dysfunction (B) Signup and view all the answers

Which illicit drug is noted for potentially causing hypoxia in the fetus?

Cocaine (B) Signup and view all the answers

What is the primary concern related to cigarette smoking during pregnancy?

Intrauterine growth retardation (B) Signup and view all the answers

Which of the following drugs has been cautioned against due to potential harm during pregnancy?

Tetracyclines (D) Signup and view all the answers

What classification does fetal alcohol spectrum disorder (FASD) encompass?

Any alcohol-related defects (B) Signup and view all the answers

What is the main purpose of maternal serum screening?

To assess fetal well-being noninvasively (C) Signup and view all the answers

At what gestational age is amniocentesis typically performed?

14 weeks or later (B) Signup and view all the answers

What is the primary risk associated with chorionic villus sampling (CVS) compared to amniocentesis?

Higher fetal loss rate (C) Signup and view all the answers

Why are prenatal diagnostic tests like amniocentesis and CVS not typically used routinely?

They are reserved for high-risk pregnancies (A) Signup and view all the answers

What is one of the significant reasons for conducting prenatal diagnostic testing?

To identify advanced maternal age (C) Signup and view all the answers

Which of the following substances is analyzed during an amniocentesis?

Acetylcholinesterase (D) Signup and view all the answers

What complication is associated with chorionic villus sampling?

Potential limb reduction defects (B) Signup and view all the answers

Which method allows for quicker genetic characterization of the fetus?

Chorionic villus sampling (CVS) (D) Signup and view all the answers

What is a syndrome in the context of birth defects?

A group of anomalies occurring together with a known specific cause (B) Signup and view all the answers

What distinguishes an association from a syndrome?

Associations are nonrandom occurrences of anomalies with an undetermined cause (D) Signup and view all the answers

During which period of gestation is susceptibility to teratogenesis the highest?

Weeks 3 to 8 of gestation (D) Signup and view all the answers

What is a key factor that affects the manifestations of abnormal development?

The dose and duration of exposure to a teratogen (B) Signup and view all the answers

Which of the following is NOT a manifestation of abnormal development due to teratogenesis?

Cognitive enhancement (C) Signup and view all the answers

What role does the maternal genome play in teratogenesis?

It affects drug metabolism and resistance to infections (A) Signup and view all the answers

What is an example of a destructive factor leading to disruptions?

Amniotic bands (B) Signup and view all the answers

Which infectious agent was historically significant for causing birth defects?

Rubella (A) Signup and view all the answers

Study Notes

Birth Defects

Birth defect, congenital malformation, and congenital anomaly are synonymous terms for structural, behavioral, functional, and metabolic disorders present at birth.
Teratology and dysmorphology are terms used to describe the study of birth defects. Dysmorphologists frequently work in clinical genetics departments.
Major structural anomalies occur in 2% to 3% of liveborn infants; an additional 2% to 3% are identified by age 5. This totals 4% to 6%.
Birth defects are the leading cause of infant mortality, accounting for approximately 21% of infant deaths. They are the fifth leading cause of years of potential life lost before age 65, and a significant contributor to disabilities.
In 40% to 60% of cases with birth defects, the cause is unknown. Contributing factors include genetics (chromosome abnormalities and mutant genes, approximately 15%), environmental factors (approximately 10%), a combination of genetic and environmental factors (20% to 25%), and multiple births (0.5% to 1%).

Types of Abnormalities

Malformation: Occurring during the formation of structures (e.g., organogenesis) during the third to eighth weeks of gestation; caused by environmental and/or genetic factors.
Deformation: Resulting from prolonged mechanical forces molding a part of the fetus (e.g., clubfoot); caused by compression in the amniotic cavity; often involves the musculoskeletal system and may be reversible postnatally.
Disruption: Resulting in morphological alteration of already formed structures due to destructive processes (e.g., vascular accidents leading to bowel atresia, amniotic bands).

Risk of Birth Defects During Gestation

A graph displays an increasing risk of birth defects occurring during the embryonic and fetal periods of gestation.

Syndromes and Associations

Syndrome: A group of anomalies occurring together with a specific common cause. This indicates a diagnosis is made, and recurrence is known.
Association: The nonrandom appearance of two or more anomalies occurring more frequently than by chance, but with an unknown cause. (E.g., VACTERL association: vertebral, anal, cardiac, tracheoesophageal, renal, and limb anomalies).

Principles of Teratology

Susceptibility: Depends on the genotype of the conceptus and the interaction with the environment. Maternal genome impacts drug metabolism, infection resistance, and biochemical/molecular processes in the conceptus.
Susceptibility Variations: Varies with the developmental stage at the time of exposure, with the third to eighth week of gestation being most sensitive.
Manifestations: Depend on the dose and duration of exposure to the teratogen.
Mechanism: Involves ways teratogens affect cells and tissues, initiating abnormal embryogenesis (pathogenesis); may inhibit biochemical/molecular processes, cause cell death, decreased cell proliferation, or other cellular phenomena.
Manifestations: Include death, malformation, growth retardation, and functional disorders.

Infectious Agents

Rubella, a serious concern historically, now has a significantly low incidence due to vaccines (approx 85% immunity).
Cytomegalovirus (CMV) is a serious threat; can be devastating for the fetus, frequently resulting in death or severe mental retardation. Maternal infections often exhibit no symptoms.
Herpes simplex virus (HSV), varicella virus, and HIV can also cause birth defects.

Other Viral Infections and Hyperthermia

Malformations can also occur after maternal exposure to measles, mumps, hepatitis, poliomyelitis, echovirus, coxsackie virus, or influenza virus. Prospective studies suggest the rates after exposure are usually low.
Toxoplasmosis and syphilis can cause birth defects. Poorly cooked meat, domestic animals (especially cats), and feces in contaminated soil can transmit the parasite. A characteristic feature in fetal toxoplasmosis infection is calcification.

Radiation

Ionizing radiation kills rapidly proliferating cells and is a potent teratogen, producing various birth defects depending on the dose and gestational stage at the time of exposure. Exposure to nuclear explosions carries a high risk for congenital defects.

Chemical Agents

Pharmaceutical drugs' contribution to birth defects is difficult to assess; there are many drugs taken during pregnancy and most studies are retrospective.
Thalidomide, an antinauseant and sleeping pill, was found to be teratogenic in 1961, causing widespread limb abnormalities.
Other chemical agents include anticoagulants (warfarin), antihypertensives (ACE inhibitors), propylthiouracial, potassium iodide, streptomycin, sulfonamides, antidepressants (imipramine), tetracyclines, amphetamines, quinine, and aspirin (salicylates).

Hormones

Androgenic agents: Synthetic progestins used to prevent abortion could lead to masculinization of female embryos, resulting in clitoris enlargement and labioscrotal fusion.
Oral contraceptives: Low teratogenic potential, but use should be discontinued if pregnancy is suspected due to other hormones producing abnormalities.
Cortisone: Studies indicate it is a teratogenic agent when injected into mice and rabbits during pregnancy, causing a high incidence of cleft palates; there is not enough evidence to link it to birth defects in humans.

Maternal Disease

Diabetes: Disturbances in carbohydrate metabolism in diabetic mothers can cause stillbirths, neonatal deaths, large infants, and congenital malformations; risk is 3-4 times higher for offspring.
Risk for malformations is also seen in non-insulin-dependent and gestational diabetes because of possible alteration in maternal glucose metabolism. Oral hypoglycemics, like biguanides and sulfonylureas, may also be teratogenic.

Nutritional Deficiencies

Many nutritional deficiencies (particularly vitamin deficiencies), shown to be teratogenic in animals, have sparse evidence in humans. Endemic cretinism from iodine deficiency is an exception. Insufficient maternal nutrition leads to low birth weights and potential defects.

Obesity

Prepregnancy obesity (>30 kg/m2 BMI) is associated with a two-to-threefold increased risk of neural tube defects, and possible birth defects. Maternal metabolic disturbances affecting glucose and insulin levels may be causative factors. Other outcomes are heart defects, omphalocele, and multiple anomalies.

Hypoxia

Hypoxia can lead to congenital malformations in various animals. However, there's limited evidence regarding humans and altitude.

Heavy Metals

Mercury-contaminated seed corn and fungicides have been linked to birth defects and increased abortions, and lead to growth retardation and neurological disorders.

Male-mediated Teratogenesis

Exposure to chemicals (ethylnitrosourea, radiation), solvents, alcohol, cigarette smoking, and other environmental factors can cause mutations in male germ cells leading to spontaneous abortion, low birth weight, and birth defects in offspring.
Advanced paternal age is a risk factor for defects.