Congenital malformations

Question 1

What are the causes of congenital abnormalities?

Answer 1

1) Genetic factors
- Chromosomal abnormalities, mutations (like Down syndrome)

2) Environmental factors
- Drugs, chemicals, viruses (like Fetal alcohol syndrome)

3) Multifactorial inheritance
- Genetic and environmental factors together

Question 2

What are the types of congenital abnormalities?

Answer 2

1) Malformation
- During organogenesis (3-8weeks)
- Complete/partial absence of a structure (environmental or genetic)

2) Disruption
- Alteration of already formed structures

3) Deformation
- Prolonged mechanical force that molds the fetal structures

4) Syndrome
- Group of anomalies due to a common cause

Question 3

What are the features of a child with fetal alcohol syndrome?

Answer 3

1) Indistinct philtrum (depressed area in the upper lip)

2) Thinner upper lip

3) Depressed nasal bridge

4) Short nose

5) Flat midface

Question 4

What is an example of malformation?

Answer 4

• Occurs during week 3-8
• Like phocomelia, (incomplete bone development therefore short limbs), were commonly associated with the drug thalidomide “thalidomide disaster”

Question 5

What is an example of disruption?

Answer 5

• Alteration in already formed structures, like the defects formed by the amniotic bands (strands in the amnion form and wraps around fingers or toes):

1) Cleft lip (lips unable to fuse due to the amniotic bands)
2) Toe amputation
3) Finger amputation

they are due to unknown reasons

Question 6

What is an example of deformation?

Answer 6

• Prolonged mechanical force that molds the fetal structures

1) Abnormal lower limb positioning
2) Clubfeet

Probably caused due to oligohydramnios (too little amniotic fluid)

Question 7

Which period is considered as the critical period?

Answer 7

Organogenesis period (week 3-8)

• Any abnormality before week 3 would lead to spontaneous abortion

Question 8

How do you calculate the pregnancy week from the LMP?

Question 9

What is the organ with the highest critical period?

Answer 9

CNS, Neural Tube Defects (NTD), week 3-18

Question 10

What are the heart abnormalities that could arise and when?

Answer 10

1) TA
2) ASD
3) VSD

Week 3-6

Question 11

During which weeks a cleft lip might happen?

Answer 11

week 5-6

Question 12

During which weeks can an abnormality in the eyes occur?

Answer 12

week 4-8

• Micropthalmia, cataract, glaucoma

Question 13

What is meant by teratogens?

Answer 13

Substances that might cause developmental disruption in embryo

Question 14

What is meant by teratology?

Answer 14

Study of factors determining the capacity of any agent (teratogen) to produce birth defects /congenital malformation or anomaly:

1) Infectious agent
2) Drug
3) Chemicals
4) Radiation

Question 15

What are the prenatal diagnosis methods?

Answer 15

detect malformation, genetic abnormalities, fetal growth, placental or uterine abnormalities

1) Noninvasive
- Ultrasound

2) Invasive:
- Chorionic villus sampling
- Maternal serum screening
- Chorionic villous sampling

Question 16

When is an ultrasound done?

Answer 16

6 weeks onwards

Question 17

What are the features of an ultrasound?

Answer 17

Uses high-frequency sound waves

it is harmless to both the fetus and the mother

Question 18

What are the things that are measured by an ultrasound?

Answer 18

1) Crown Rump Length (CRL)
2) Bi-Parietal Diameter (BPD)
3) Femur Lenght (FL)
4) Abdominal circumference & its defects
5) Neural tube defects
6) Facial defects
7) Nuchal Translucency (NT “Translucent area behind the neck”), detects Down syndrome (11-14 weeks)
8) Gestational age
9) Position of the fetus and placenta
10) Amount of amniotic fluid

Question 19

Describe the maternal serum screening

Answer 19

It is a test that checks for biochemical markers in maternal blood, particularly Alfa-FetoProtein (AFP) 14 weeks onwards, it is produced by the fetal liver and can cross the placenta entering maternal blood, Normal AFP levels is 1.0, an increase in AFT indicates neural tube defects while a decrease in it can be an indicator of down syndrome

Question 20

Describe the process of amniocentesis

Answer 20

• Fetal skin cells are floating within the amnion
• Needle is pierced into the amnion and a sample of it is withdrawn ideally between weeks14-20
• Cells are then grown in culture for chromosomal, biochemical, and molecular biology analysis
• Make sure that you do not pierce the placenta, and you can do that using an ultrasound

Question 21

Describe what is a chorionic villus sampling

Answer 21

• Cathered is passed through the cervix into the uterus you can also pass it through the abdomen
• Sample cells from the placentalchorionic villi for the chromosomal analysis of the fetus

Question 22

When do we need to do one of the diagnostic methods?

Answer 22

1) Advanced maternal age

2) Previous child with a chromosomal abnormality

3) Family history of a chromosomal abnormality

4) Family history of a single-gene disorder

5) Family history of congenital structural abnormality

6) Abnormalities identified in pregnancy

7) Other risk factors (consanguinity, poor obstetric history)

Question 23

What are the measures of birth defects?

Answer 23

1) Mother takes Iodine to prevent fetal Cretinism

2) Strict diet control for diabetic mothers

3) Folate supplementation prevents neural tube defects

4) Avoidance of teratogen (alcohol, smoking, drugs)

5) Early treatment for Syphilis

6) Recommended vaccinations (Tdap)