Congenital malformations Flashcards
What are the causes of congenital abnormalities?
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
What are the types of congenital abnormalities?
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
What are the features of a child with fetal alcohol syndrome?
1) Indistinct philtrum (depressed area in the upper lip)
2) Thinner upper lip
3) Depressed nasal bridge
4) Short nose
5) Flat midface
What is an example of malformation?
- Occurs during week 3-8
- Like phocomelia, (incomplete bone development therefore short limbs), were commonly associated with the drug thalidomide “thalidomide disaster”
What is an example of disruption?
- 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
What is an example of deformation?
- Prolonged mechanical force that molds the fetal structures
1) Abnormal lower limb positioning
2) Clubfeet
Probably caused due to oligohydramnios (too little amniotic fluid)
Which period is considered as the critical period?
Organogenesis period (week 3-8)
- Any abnormality before week 3 would lead to spontaneous abortion
How do you calculate the pregnancy week from the LMP?
What is the organ with the highest critical period?
CNS, Neural Tube Defects (NTD), week 3-18
What are the heart abnormalities that could arise and when?
1) TA
2) ASD
3) VSD
Week 3-6
During which weeks a cleft lip might happen?
week 5-6
During which weeks can an abnormality in the eyes occur?
week 4-8
- Micropthalmia, cataract, glaucoma
What is meant by teratogens?
Substances that might cause developmental disruption in embryo
What is meant by teratology?
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
What are the prenatal diagnosis methods?
detect malformation, genetic abnormalities, fetal growth, placental or uterine abnormalities
1) Noninvasive
- Ultrasound
2) Invasive:
- Chorionic villus sampling
- Maternal serum screening
- Chorionic villous sampling
When is an ultrasound done?
6 weeks onwards
What are the features of an ultrasound?
Uses high-frequency sound waves
it is harmless to both the fetus and the mother
What are the things that are measured by an ultrasound?
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
Describe the maternal serum screening
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
Describe the process of amniocentesis
- 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
Describe what is a chorionic villus sampling
- 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
When do we need to do one of the diagnostic methods?
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)
What are the measures of birth defects?
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)
