Every parent hopes to have a healthy child. The good news is most babies are born healthy. However, some families planning to have children may be faced with the diagnosis of a genetic disease. Genetics contributes up to 10 percent of infertility issues or recurrent pregnancy losses in couples. Most embryos with an incorrect number of chromosomes fail to implant or miscarry during early trimester of pregnancy. Genetic testing protocols have the potential to help many of those couples in their quest to have a family. It is seen that about 50 to 70 percent of cleavage stage embryos produced in vitro are chromosomally abnormal. This is much higher than that of spontaneous abortions. Data shows that in women of advanced maternal age (AMA), decline in pregnancy is largely caused by failing oocyte quality. The most common syndromes caused by chromosome abnormalities are Down syndrome, Edwards syndrome and Patau syndrome ( Chromosome 21, Chromosome 18, Chromosome 13 respectively)
PGD or PGS are the techniques which allow selection of normal embryos for replacement thus, increase implantation rates, reduce spontaneous abortion rates, reduce aneuploid conceptions , and improve delivery rates in ART cycles. PGS/PGD include genetic tests on cells removed from embryos, to help select the best embryo(s) to achieve pregnancy or to avoid a genetic disease for which a couple is at risk. A laser beam is used to create a small hole in the zone pellucida (covering of the embryo) and few blastomeres are biopsied usually at blastocyst stage . The cells are fixed on a slide and chromosomes analyzed.
PGS is a genetic test performed on embryos to identify numerical chromosomal abnormalities (aneuploidy).The test is performed on embryos before transfer to the uterus.By analysing all embryos generated in an IVF treatment cycle those free of chromosomal aneuploidy can be selectively transferred. As a result, the pregnancy rates per transfer are significantly increased and the miscarriage rates decreased. PGS analyses all 24 chromosome types , selects chromosomally normal embryos for transfer which are most likely to develop to term and to be born as a healthy baby. Where chromosomal PGS testing is performed, one can expect fewer pregnancies ending in miscarriages due to chromosomal disorders since most abnormalities are identified prior to transfer of the embryos to the uterus. We use the most advanced technology, NGS (Next-Generation Sequencing) & using array Comparative Genomic Hybridisation (aCGH), to perform the PGS test. It is a rapid technology allowing embryos to be transferred in fresh or frozen cycles and demonstrates ability to detect aneuploidies, mosaicism and segmental alterations.
Removal of a few of the trophectoderm cells of the early embryo does not alter the ability of that embryo to develop into a complete, normal pregnancy. Data from many years of PGS/PGD in animals and several hundred thousand live births in humans indicate that PGS/PGD does not lead to an increase in birth defects over that of the general population. Follow-up evaluation of children born after PGS/PGD does not show any evidence for a detrimental effect of the process on growth or neurological development over the first several years of life.
There are some other indications for using PGS with infertility and they are as follows :
Advanced age of woman > 35years age
Recurrent pregnancy loss (RPL) It can reduce spontaneous abortions in patients with idiopathic RPL
Repeated implantation failure (RIF)( Multiple failed IVF attempts)
Severe oligoasthenozoospermia in males
Couples with previous pregnancy with chromosomal abnormality
Cases where SET ( single embryo transfer ) is contemplated.
Preimplantation Genetic Diagnosis in infertility ( PGD)
- While PGD also analyzes a small piece of the embryos( Blastomere Biopsy) during an IVF cycle to detect genetic alterations, it is focused on single gene diseases or mutations. It prevents transmission of single gene disorders in a family in order to achieve a healthy pregnancy.
- It’s performed on the embryo before it is transferred to the uterus, as part of an assisted reproduction treatment. Through analysis of the embryos, it is possible to select those that are free from the disorder. In these cases only targeted, particular chromosomal abnormalities are looked for, based on the previous history.
- PGD helps couples who have an increased risk for a genetic disease to conceive a healthy pregnancy in addition to screening for all genetic diseases. PGD can be useful in cases of any recognized monogenic disease.
- Common examples of monogenic disorders are cystic fibrosis, fragile X syndrome, spinal muscular dystrophies (SMA), Duchenne muscular dystrophy (DMD), Huntington disease. For couples with family history of monogenic diseases such as Alpha Thalassemia, Glycine encephalopathy, Familial mediterranean fever, Haemochromatosis, Polycystic kidney, etc, we can move ahead to do PGD testing.
- The combination of normal genetic testing with normal physical appearance indicates the highest chance of becoming a healthy pregnancy. All decisions regarding which embryo(s) to transfer to the uterus and how to use the remaining embryos are made together between the couple and their medical team. Using direct detection, PCR is used to detect the specific disease causing mutation, in linkage analysis PCR is used to detect informative STR markers that are linked to the disease-causing gene. Thus multiple detection minimizes risk of Allele drop outs and misdiagnosis and is > 98% accurate.
Our comprehensive list of reproductive genetic testing services at Anmol Fertility & IVF Centre thus handholds you through the tiring journey of finding truths to seemingly unanswerable issues & can greatly increase your chances of becoming a mother.