PGD is offered for couples who are at risk of having children with serious genetic disorders (such as Down's Syndrome) and sex linked disorders such as hemophilia, thallasaemia etc. This new technique will also increase the chances for success of the IVF/ICSI (test-tube baby) program.
PGD technique involves testing of early stage embryos for chromosomal abnormalities such as Down's Syndrome, so that only healthy embryos are selected for transfer into the mother's womb. It also allows the determination of sex of the embryos, in particular for conditions with a sex-linked disorder, so that only embyros of certain sex without inherited disease are selected for transfer into the mother's womb.
Patients would have to undergo an IVF (test-tube baby) program in order to have PGD performed. After the eggs are fertilized in the laboratory, the embryos are biopsied for further investigation of abnormal conditions as mentioned above before being transferred into the womb. Blastomere Biopsy and Preimplantation Genetic Diagnosis (PGD) - Fluorescent In Situ Hybridization (FISH).
We are able to detect chromosomal abnormalities caused by various chromosomes including:
Condition |
Frequency |
Syndrome |
Characteristic |
Trisomy 21 |
1/800 |
Down Syndrome |
Mental retardation, abnormal pattern of palm creases, slanted eyes, flattened face, short stature |
Trisomy 18 |
1/6000 |
Edward Syndrome |
Mental and physical retardation, facial abnormalities, extreme muscle tone, early death |
Trisomy 13 |
1/15000 |
Patau
Syndrome |
Mental and physical retardation, wide variety of defects in organs, large triangular nose, early death |
XXY |
1/1000(male) |
Klinefelter
Syndrome |
Sexual immaturity (no sperm), breast swelling |
XYY |
1/1000(male) |
Jacobs
Syndrome |
Tall, high risk of learning difficulties and behavioural problems. |
XXX |
1/1500(female) |
Triple X |
Tall and thin, menstrual irregularity |
XO |
1/5000(female) |
Turner
Syndrome |
Short stature, webbed neck, sexually undeveloped. |
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The picture of the cell under the FISH microscope. Result of the analysis is a normal male embyro (XY) |
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The picture of the cell under the FISH microscope. Result of the analysis is a normal female embyro (XX) |
PGD - Screening for Beta-Thalassaemia
Thalassaemia is an inherited condition causing various degree of anaemia (low level of haemoglobin). This disease is unfortunately prevalent in South East Asia, especially among the Chinese. When both parents are carriers of beta-thalassaemia and plan to have their baby, the chances of the getting a normal baby is 25% .
Traditional prenatal diagnosis is performed by amnioncentesis at 15 to 16 weeks of gestation. If the baby was found to be affected by thalassaemia, the couple will be facing a painful decision to have abortion. PGD-PCR for B-thalassaemia screening allows at-risk couple to have only unaffected embryos transfer. We are one of the few centres that screen for this condition. After undergoing IVF, some genetic material was removed from the embryos derived from the affected couple. The genetic material is multiplied using Polymerase Chain Reaction (PCR), and only healthy embryos free from thalassaemia will be transferred, ensuring the baby born to be free from thalassaemia.
Preimplantation Genetic Screening (PGS)
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