Prenatal Genetic Screening for Embryo Adoption

The most common test performed is the determination of the chromosomal composition of the embryos. This is referred to as aneuploidy testing. Each normal embryo contains 46 chromosomes, 23 of which are contributed by the sperm and 23 by the egg. An embryo that contains 46 normal chromosomes is called a euploid embryo. An embryo that has more or less than 46 chromosomes is called an aneuploid embryo. There are two types of chromosomes, the sex chromosomes (X and Y), which determine the gender of the embryo, and the autosomes (1-22), which determine almost everything else. The autosomes are normally present in pairs. The sperm contributes one sex chromosome (X or Y) and 22 autosomes. The egg contributes one sex chromosome (X only) and 22 autosomes. Sometimes microarray is referred to as 24-chromosome microarray: 22 chromosomes, and X and Y are counted as one each, for a total of 24.

The process of screening embryos for genetic abnormality has become much more useful because of a new technology called 24-chromosome microarray. It is now possible to determine the complete chromosomal composition of an embryo, (that is all 24) from testing a single cell. Each chromosome is composed of two strands of DNA that are chemically attracted to each other in a way that holds them together for their entire length. These two strands of DNA are referred to as complementary strands and it is the chemical attraction between complementary strands that is the basis for testing chromosomes with microarray.

Among the many improvements to historical methods of PGS, new technology, termed comprehensive chromosome screening (CCS), provides information for the normality of all 23 chromosomes pairs. Unlike previous methods, Comprehensive Chromosome Screening prevents the selection and transfer of abnormal embryos for unscreened chromosomes and has powerful evidence of improving ART outcomes. The most common PGS protocol used today is to biopsy the embryo on the fifth day (trophectoderm-precursor of the placenta biopsy) after the egg has been fertilized.

Humans have 23 pairs of chromosomes, inheriting one copy of each chromosome from each parent. When an embryo is created, it should consist of 23 chromosomes from the egg and 23 chromosomes from the sperm. An abnormality in an embryo's chromosomal configuration may cause a specific syndrome to occur in the offspring or may cause the pregnancy to miscarry. Sometimes embryos are created with too many or too few chromosomes—a condition known as aneuploidy. Aneuploidy is a major contributor to miscarriage, in vitro fertilization (IVF) failure, and various health conditions, including Down syndrome. This technology has the potential for doctors to select embryos free of that specific chromosomal problem in order to create healthy babies or to select the sex of the embryos being transferred for family balancing. CCS should make the chance of a healthy live birth from a single embryo transfer of a known chromosomally normal embryo very high while minimizing the chance of multiples.

The process includes a biopsy of the embryo and comprehensive chromosomal screening (CCS) to screen the embryos for chromosomal abnormalities, followed by revitrification of the embryos to get the test results and transferring unaffected embryos in a frozen embryo transfer cycle (FET).

HOW SAFE AND ACCURATE IS IVF - CCS?

Considering that the determination of the well-being of an embryo in a Day 5 biopsy is being made on the basis of the evaluating the chromosomes in just a few cells of a >100-200 cell embryo and the results are being interpreted very rapidly, the estimated misdiagnosis rate using CCS for aneuploidy is remarkably low (< 0.01%). A misdiagnosis may occur if the cells removed are not representative of the major cell line in that embryo. With IVF/CCS, embryos can be screened in the laboratory for a specific chromosomal problem and only embryos thought not to be affected with the condition in question are transferred into the mother.

WHAT IS THE ALTERNATIVE TO IVF - CCS?

The alternative to IVF - CCS is for a couple to achieve a pregnancy naturally, or through conventional fertility treatment, and to rely on prenatal diagnosis through chorionic villus sampling (CVS) or amniocentesis using similar molecular diagnostic techniques.

How to get started with Embryo Adoption/Embryo Donation?

We encourage you to contact our office to schedule an appointment with our physicians to discuss this and all fertility therapy/treatment options AEAA has to offer. We want to get to know you and hear the dreams you have for your future family. We'd be happy to give you more information and answer any questions you might have. Our objective is to assist every AEAA patient with achieving their goal of starting or enlarging their family. We do our best to ensure patients have a clear understanding of their treatment options, so they are able to choose the option that will best fit their needs. Our highly trained team of professionals is here to answer your questions and assist you with your journey. If you are interested in Embryo Adoption, please feel free to contact us by calling (615) 856-0581.

 

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