Genetic Conselling

Question 1

Genetic Counselling

Answer 1

A process of communication that deals with the occurrence/ risk that a genetic disorder will occur in a family.

Question 2

Criteria for a genetic screening programme

Answer 2

1. Pregnant women over 35- for chromosomal abnormalities
2. Families with 1 child with a genetic disorder/ birth defect.
3. Closely related couples (i.e., first cousins)
4. Women who had two/ more miscarriages/ who had babies die in infancy.

Question 3

Maternal serum screening (non-invasive prenatal testing)

Answer 3

Hormonal levels of the mother found in the blood are tested, to identify Down Syndrome, indicated by low alpha-fetoprotein (Afp) and unconjugated estriol (UE3) and high levels of Human Chorionic gonadotropin (hCG)
- Increased alpha-fetoprotein (Afp) indicates Neural tube defect.
- Triple test is done at 16 weeks (2nd trimester)

Question 4

Ultrasonography (non-invasive prenatal testing)

Answer 4

Echoes reflected from organ boundaries are converted into images on a monitor. This test is used to check for physical abnormalities, e.g., Anencephaly @ 10-12 weeks and trisomy 18 @ 18-20 weeks

Question 5

Amniocentesis (invasive prenatal testing)

Answer 5

It is a test offered to check for genetic/chromosomal conditions during pregnancy.
-It’s done 16-18 weeks of pregnancy
- It’s done by localizing the placenta, inserting a needle, guided by ultrasonography, aseptically through the mother’s abdominal wall into the amniotic cavity and drawing 10-20 ml of the amniotic fluid. Cells from the fetuses found in the amniotic fluid will take 14 days to culture before karyotyping, foetal sexing and enzyme assay.
-it is best to use to identify sex-linked traits, if abnormalities are found the parents are facing a possibility of late mid-trimester termination of the pregnancy, which involves induction labour.
- The testing procedure is the safest invasive prenatal testing with a miscarriage risk of 0.5-1%

Question 6

Chorionic Villus Sampling (CVS) (invasive prenatal testing)

Answer 6

-The earliest prenatal testing, done @ 10-12 weeks of pregnancy.
-It is done by inserting a catheter through the cervix or by trans-abdominal puncture guided by ultrasonography.
-because the nuclei from the biopsy divide rapidly, culturing to karyotype won’t be needed.
-With the risk of miscarriage being 0.5-2% there is also a risk of the fetus developing limb abnormalities if the testing is done before 9 weeks of gestation.