12.0 Prenatal Diagnosis

Question 1

What is the inheritance pattern of the following:<br></br><br></br>1) Cystic fibrosis<br></br>2) Myotonic dystrophy<br></br>3) Duchenne muscular dystrophy<br></br>4) Congenital adrenal hyperplasia<br></br>5) Huntington disease

Answer 1

<b>1) Cystic fibrosis</b> - AR<br></br><b>2) Myotonic dystrophy</b> - AD<br></br><b>3) Duchenne muscular dystrophy</b> - XLR<br></br><b>4) Congenital adrenal hyperplasia</b> - AR<br></br><b>5) Huntington disease</b> - AD

Question 2

What are the 2 main neural tube defects?

Answer 2

1) Anencephaly<br></br>2) Spina bifida

Question 3

What is anencephaly caused by?

Answer 3

Failure of closure of anterior neuropore

Question 4

What is spina bifida caused by?

Answer 4

Failure of closure of posterior neuropore

Question 5

What are open neural tube defects?

Answer 5

The neural tissues and meninges are exposed<br></br>Occurs in 100% of anencephaly<br></br>Occurs in majority of spina bifida<br></br>Maternal serum has ↑ Alpha fetoprotein

Question 6

What are closed neural tube defects?

Answer 6

Skin covers defect<br></br>15-20% of spina bifida<br></br>Not detectable biochemically (No ↑ in alpha fetoprotein)

Question 7

What can reduce incidence of neural tube defects?

Answer 7

Folic acid

Question 8

What is Trisomy 21?

Answer 8

Down’s syndrome

Question 9

What translocation can cause Down’s syndrome?

Answer 9

14:21

Question 10

What percentage of Trisomy 21 are primary trisomy and what percentage are due to translocation?

Answer 10

Primary trisomy = 95%<br></br>Translocation = 5%

Question 11

Signs + symptoms of Down syndrome:

Answer 11

<b>• Intellectual disability</b> (mild-moderate learning difficulties)<br></br><b>• Dysmorphic</b><br></br> o Flat nasal bridge<br></br> o Up slanting palpebral fissures<br></br> o Epicanthic folds<br></br> o Protruding tongue<br></br> o Single palmer crease<br></br> o Clinodactyly<br></br> o Sandal gap<br></br><b>• Cardiac defects</b><br></br> o 40% of cases

Question 12

What is Trisomy 18?

Answer 12

Edward syndrome

Question 13

Signs + symptoms of Edward syndrome:

Answer 13

• Intellectual disability (severe)<br></br>• Dysmorphic<br></br> o Micrognathia<br></br> o Prominent occiput<br></br>• Clenched + overlapping fingers<br></br>• Prominent heels and rocker-bottom feet<br></br>• Cardiac defects<br></br><br></br><br></br>Most die before 1yr

Question 14

What is Trisomy 13?

Answer 14

Patau syndrome

Question 15

Signs + symptoms of Patau syndrome:

Answer 15

• Mental disability (severe)<br></br>• Dysmorphic<br></br> o Cleft lip + palate<br></br> o Holoprocencephaly<br></br> o Postaxial polydactyly<br></br>• Renal abnormalities<br></br>• Cardiac defects<br></br><br></br>Most die before 1yr

Question 16

What are sex chromosomes in Turner syndrome?

Answer 16

XO

Question 17

What are sex chromosomes in Klinefelter syndrome?

Answer 17

XXY

Question 18

What conditions cause increase nuchal translucency (NT) thickness measurements?

Answer 18

1) Trisomy 21<br></br>2) Cardiac defects<br></br>3) Venous congestion of head and neck<br></br>4) Abnormal lymph development<br></br>5) Neuromuscular disorders<br></br>6) Fetal anaemia<br></br>7) Congenital infection

Question 19

What conditions cause a lemon or banana sign on ultrasound?

Answer 19

1) Spina bifida<br></br>2) Chiari II malformation

Question 20

What conditions cause increase in maternal serum alphafetoprotein levels?

Answer 20

1) Neural tube defects (open)<br></br>2) Trisomy 21

Question 21

What serum markers increase with trisomy 21?

Answer 21

<b>1) Alphafetoprotein</b><br></br><b>2) Unconjugated estriol</b><br></br><b>3) hCG</b> (largest increase)

Question 22

Risk of miscarriage with chorionic villus sampling?

Answer 22

1-2%

Question 23

Risk of miscarriage with amniocentesis?

Answer 23

0.5%