PGD - Preimplantation Genetic Diagnosis
PGD, or PreImplantation Genetic Diagnosis, is a new technique pairing Molecular Genetics with Assisted Reproductive Technology (ART). Malpani Infertility Clinic was the first clinic to offer this service in India, and has achieved India's first pregnancy after PGD.
Malpani Infertility Clinic is very pleased to be able to provide the facility of PGD - preimplantation genetic diagnosis - the newest ART- for the first time in India. We are the only clinic which offers this service in India, and have achieved India's first pregnancy after PGD.
PGD, or preimplantation genetic diagnosis, is a new technique , which marries the recent spectacular advances in molecular genetics and assisted reproductive technology (ART) . Preimplantation genetic diagnosis enables physicians to identify genetic diseases in the embryo, prior to implantation, before the pregnancy is established. PGD was developed for patients who were at risk of having children with serious genetic disorders , such as hemophilia, which often discouraged them having their own biological children. These couples are often faced with attempting a type of "Russian Roulette" to have children, many times having to confront the difficult decision to terminate an affected pregnancy. Consider a woman known to be carrying the gene for hemophilia . She has a 50% risk of an affected male in each pregnancy. While her daughters have a 50% risk of being carriers , they are going to be clinically normal. She may not wish to become pregnant if she has to make decisions about an affected child in a viable pregnancy. However, she would become pregnant if she knew she had conceived a daughter - and with preimplantation diagnosis this possibility becomes a reality. PGD thus eliminates the need for possible pregnancy termination after prenatal diagnosis of a fetus with hemophilia.
In order to perform PGD , we have to do IVF (in vitro fertilisation). In an IVF cycle, treatment starts from Day 1 of the cycle (the day the bleeding starts). We superovulate you in order to help you grow many eggs, and this is done by giving you daily injections of HMG. Once the eggs are mature , as determined by ultrasound scans, (this usually takes about 12-14 days ) we retrieve the eggs. This is done through vaginal ultrasound guidance, and no surgery is required. The eggs are then fertilised, and on Day 3, the embryos are biopsied to determine their genotype. Only the normal embryos are then transferred into the uterus, which means that if you conceive you are sure that your baby will be normal !
Click here if you want to see how the procedure of embryo biopsy is performed in our lab.
The babies born after PGD are completely normal; and IVF treatment is extremely safe today. The hormonal injections required to make you grow many eggs will not make you fat , and neither will they affect your future fertility ! In fact, the major risk of doing PGD today is that even after spending all the money (and treatment can be expensive !), there is no certainty that a pregnancy will result. This is because while we can make embryos efficiently in the IVF lab , and determine their genotype accurately in the FISH lab, we still cannot ensure that the embryos will implant successfully after transferring them into the uterus.
The pregnancy rate in our clinic after performing PGD for women who are less than 35 years of age, in whom we have transferred 3 embryos , is 40%.Top
Analysis of genetic material (DNA) from a single cell is performed using a technique called FISH (fluorescent in situ hybridisation) . FISH utilises fluorescent probes, which are specific for a given chromosome, and therefore allows one to screen embryos for chromosomal normality. FISH probes are commercially available and are manufactured by Vysis, USA. For example, the Vysis AneuVysion 18/X/Y probe allows us to check for the number of chromosomes 18 , X and Y, using a fluorescent microscope. During the analysis on the single cell, the embryos are kept in culture and allowed to further divide. Only normal embryos are then replaced in the uterus.
Fig 1. Direct (uncultured) amniocyte hybridized with the AneuVysion 18/X/Y probe. Three aqua (blue dots) signals indicate three copies of chromosome 18, one green signal (green dot) indicates one copy of chromosome X and one orange signal (orange dot) indicates one copy of chromosome Y. This is an abnormal embryo and would not be replaced.
Fig 2. CEP X Spectrum Orange / CEP Y (Satellite III) SpectrumGreen hybridized to lymphocytes.
Fig 3. The FISH probes are available as a "ready-to-use" kit from Vysis, USA.
- Munné S, Tang YX, Grifo J, Rosenwaks Z, Cohen J. Sex determination of human embryos using the polymerase chain reaction and confirmation by fluorescence in situ hybridisation. Fertil Steril 1994;61:111-7.
- JC Harper, E Coonen, FC Ramaekers, JD Delhanty, AH Handyside, RM Winston, and AH Hopman Identification of the sex of human preimplantation embryos in two hours using an improved spreading method and fluorescent in-situ hybridization (FISH) using directly labelled probes Hum Reprod 1994 9: 721-724.
- JA Grifo, YX Tang, S Munne, M Alikani, J Cohen, and Z Rosenwaks . Healthy deliveries from biopsied human embryos . Hum Reprod 1994 9: 912-916.