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2019

Genetic Testing – Should You Have Genetic Testing For Your Embryos

Genetic Testing

Should You Have Genetic Testing For Your Embryos

With infertility treatments like IVF (in vitro fertilization), the chances of success are dependent on many factors. The woman may respond poorly to the fertility drugs, produce eggs that do not fertilize or develop chromosomally abnormal embryos. The embryo might even fail to implant successfully because the uterine lining is not thick enough. Even the procedure for retrieving and transferring eggs can potentially fail. The embryo or oocyte may also be damaged during transfer or unfreezing.

Genetic testing for eliminating chromosomal abnormalities

Dr Hishey (Indira IVF hospital), explained “Among all these factors, it is the chromosomal abnormality that determines success in most cases. In fundamental terms, almost all infertility treatments are dependent on the ovulation of multiple eggs simultaneously. For pregnancy, at least one of these eggs has to fertilize, get implanted in the uterine lining and ultimately develop into a fetus”.

Statistically, among women over the age of 35, a considerable percentage of eggs developed are of poor quality. These eggs have chromosomal abnormalities like monosomy or trisomy. These abnormalities are known to cause faulty pregnancy or even miscarriage. Thankfully, there is a way to detect these factors and eliminate them completely. It can be possible through PGT – Pre Genetic Testing.

While PGT doesn’t prevent the occurrence of chromosomal abnormalities, it does increase the chances of getting pregnant. With the help of this test, the doctors can identify aneuploids, which are errors in cell division resulting in a chromosome number that isn’t an exact multiple of a haploid number. When healthy embryos are identified, they can be transferred with total assurance. Thus, PGT can effectively eliminate chromosomal abnormalities, which increases the chances of successful pregnancy to 85%.

The possibility of identifying genetic issues during fertility treatments

Fertility treatments provide a great opportunity for detecting and preventing genetic diseases from being transmitted to the offspring. Apart from genetic screening, embryo testing can be performed as well during the fertility treatments. This helps in detecting the embryos that don’t carry the genetic disease, allowing the exclusion of unhealthy embryos.

Concerns like the genetic testing cost in India arise if there is a family or genetic history. Genetic concerns may also be encountered during the routine tests that are done before the fertility treatment. With the advancements in technology, it is now possible to identify the carriers of genetic diseases. A thorough screening test and family history can help determine the possible genetic diseases that may be transmitted. Dr. Shashibala (Gynaecologist & IVF Specialist, Indira IVF, Ranchi), revealed the common diseases test below:

Common diseases tested

  • Routine screening: This is done for both the partners trying to achieve pregnancy. The routine screening is done on common genetic issues. The ethnic ancestry of the individual involved plays a big role in determining the issues that are screened. First, only one partner is screened. If the test results are positive for the concerned partner, the other partner is tested. Cystic fibrosis and spinal muscular atrophy are commonly tested.
  • Reduced ovarian reserve: If the ovarian reserve is diminished even if the woman is young, screening needs to be done to check for Fragile X syndrome mutation. Even chromosomal abnormalities like mosaic Turner syndrome can be screened for. A karyotype-a test can be used for checking the shape and number of chromosomes.
  • Male infertility: This is the case when the male partner has very low counts of sperm or even no sperm at all. In these cases, PGT needs to be carried out to check for Cystic Fibrosis, microdeletions of Y chromosome and Klinefelter syndrome.
  • Recurrent pregnancy loss: Sometimes, a couple may report multiple pregnancy losses consecutively. If that happens, particularly in the first trimester, there is a chance that one of the partners carries a chromosomal abnormality. This can result in trisomy, a condition where an extra chromosome is transmitted to the newborn.
  • Genetic disease in the family: It may happen that either of the parent or a prior child or any family member is affected by a genetic disease. In case the disease is well defined, the individual affected needs to be tested first. This helps in determining the mutation of the DNA that causes the disease. Thereafter, the couple is checked for the mutation.
  • Chromosomal abnormality in a parent or child: If there is a chromosomal abnormality in a prior child, it is better to make sure it doesn’t reoccur in the future child. The karyotype of both the parents needs to be obtained for determining which one carries the abnormality.
  • Inherited cancer predisposition: Due to inheriting specific mutations, some people inherit a predisposition to cancer. This needs to be checked for if several family members across different generations were diagnosed with particular cancer before the age of 50. FAP gene for colon cancer and BRCA 1 and 2 for ovarian and breast cancer are examples of genetic cancer predisposition. With these mutations, there is a high risk of cancer. Thankfully, it can be detected during genetic testing with IVF and transmission to future generation can also be prevented.
  • Cancer diagnoses in a prior child: PGT can be considered for families having a child diagnosed with cancer such as retinoblastoma. First of all, the diagnosis of a specific mutation can help in preventing cancer from being transmitted to the future child. Furthermore, with some type of cancer like leukemia, bone marrow transplantation is required from a genetically close donor. Families can choose to conceive a child that compatible genetically with the sibling. The umbilical cord blood can be used to transplant a bone marrow for the diagnosed child.

Ways of testing for genetic risks

  • Genetic screening through blood tests: Analysis of the blood cells is done for detecting the carrier status. The test is carried out to check the concerned disease and helps in identifying if an individual carries a defective gene. Genetic counseling is often the right choice if the screening tests provide positive results. It informs the couple about the risk of disease being transmitted to the offspring. This allows them to make an informed decision regarding further treatments or tests.
  • DNA testing through embryo biopsy: During the cleavage stage of embryo fertilization, a single or couple of cells are removed from the embryo. The DNA of these cells are then analyzed for particular mutations. The embryos affected by the mutation are excluded while the ones deemed healthy are transferred to the uterus. Results of the DNA tests can be obtained with 1-2 days, after which healthy embryos can be transferred.

Since the genetic material that is available for these tests is small, they are screening methods and not a diagnosis. For prenatal diagnosis, genetic testing during pregnancy, generally the first or second trimester, is recommended. This diagnosis involves the mother’s blood tests, CVS or amniocentesis for testing the fetus’ genetic material.

How is PGT done?

Dr. Ruhi Srivastava (Gynaecologist & IVF Specialist, Indira IVF, Ranchi), explained, “PGT is done through the biopsy of an embryo or an egg. The chromosomes of cells are then counted. Normally, there are 22 pairs of chromosomes in cells, along with XY (male) or XX (female) chromosome, totaling to 46 chromosomes. The embryo receives one chromosome from each pair from the father’s sperm and mother’s egg. However, in some cases, the sperm or egg contains too few or too many chromosomes. This jeopardizes the viability of the embryo”.

Chromosomal abnormalities like these can occur when trying to achieve pregnancy, be it naturally or through assisted reproductive technologies like IVF. However, with a process like IVF, these abnormalities can be detected even before the pregnancy starts. If they are detected, the couple can choose not to implant the unhealthy embryos.

So, how is genetic testing done? For performing the process, a small needle is used for collecting a small sample of the embryo or egg to analyze it. Three methods are commonly used:

  • Testing the polar body from outside the egg
  • Testing a single cell (blastomere) on the third day of the egg’s development
  • Testing multiple cells (trophectoderm) on the fifth day of the egg’s development

Once the chromosomes are counted, the embryo is returned to the incubator to allow it to grow further. It can even be frozen for use in future.

Effect of the test on infertility treatment

Dr. Mekhla Goyal, (Gynaecologist & IVF Specialist, Indira IVF, Ahmedabad), explained, “The infertility treatment plan can be greatly affected by the results of the genetic tests. Sometimes, the genetic abnormality detected doesn’t require any change in the infertility treatment. This is the case with autosomal recessive diseases, with only one of the parents carrying the genetic mutation. These are the diseases that require two abnormal genes for manifesting.

In some cases, the couple in question might decide not to undergo genetic tests. It may so happen that they wish to perform these tests only after pregnancy is established. If the couple is well informed and takes the decision accordingly, the treatment plan doesn’t have to be altered.

Sometimes, however, if genetic abnormalities are detected, they require the infertility treatment plan to change. This is common when the couple carries a genetic mutation and there is a major risk of it being transmitted to their offspring. The infertility treatment may have to be altered for avoiding the transmission or minimizing the chances of it happening. A lot of times, people switch to IVF treatment as it allows testing of the embryo. It allows transfer on only the healthy embryos.

Certain genetic diseases manifest preferentially in a specific case. For example, Duchenne myopathy or Hemophilia are known to affect males more than females. These genetic issues can simply be avoided by transferring the opposite sex embryos.

Whether you want to perform embryo testing or not is completely up to you. You need to consider the genetic testing cost along with other factors that might come into play. If you are concerned about genetic disease, having your embryo tested for it can give you the peace of mind.

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