Learn More about Modern IVF Technologies
Many of you might know a little bit about what In Vitro Fertilization means, and how it has helped millions of families around the world achieve their dreams of conceiving a baby (or two). This article will pertain to certain technologies that are available to those who are undergoing In Vitro Fertilization (IVF). Maybe you have heard that now couples are able to select the gender of their future baby or perhaps choose the amount of babies they would like to have. IVF technologies can also help you determine if an embryo has any chromosomal abnormalities. Some of these technologies are:
Intracytoplasmic Sperm Injection (ICSI)
This is a procedure in which a single sperm is isolated and directly injected into the egg, creating fertilization. This technique was revolutionary when finally mastered in the late 1990s. Prior to this, men who produced few sperm or sperm with low motility (poor swimmers), required donor sperm since their sperm may not have had the capacity of burrowing through the egg’s shell appropriately. Now, although very difficult to catch a single swimming sperm with a pipette, through ICSI, fertilization can occur with a man who produces a very low sperm count.
Testicular Sperm Extraction (TESE)
This process is usually performed by a urologist who specializes in male fertility. Approximately 40 percent of men who produce no sperm have some sort of tubal obstruction (yep, sperm have to pass through a series of pipes to be ejaculated), usually in the Vas Deferens. Men who have had hernia repairs are usually at high risk for having obstructions created from surgery. Some men, especially Cystic Fibrosis carriers are born without the Vas Deferens. In these cases, there is usually ample sperm in the testis and hopefully epididymis where sperm are usually more mature. A urologist can simply extract sperm directly from the testis with a special syringe and, via ICSI, fertilize eggs extracted from the body through IVF. This process results in embryos grown in an incubator for three to five days and placed back into the uterus.
Assisted Hatching (AH)
Embryos sometimes have shells that surround them that look very thick. We believe that these thickened shells may not allow the embryo to “hatch” sometimes, preventing implantation and pregnancy. These thickened shells are notoriously encountered in Poor Responders and in women over the age of thirty-eight. The shell can be thinned out to make it easier for the embryo to hatch either through a laser or an acid solution.
Preimplantation Genetic Diagnosis (PGD)
A procedure where a specific genetic defect can be determined in embryos. A Day Three embryo usually has eight cells and one of these cells is extracted and analyzed for the specific defect. For example, a couple both are carriers for Cystic Fibrosis (CF), meaning they are at high risk for passing fulminant CF to their children. The cell that was extracted from the embryo is analyzed for CF, and if the cell doesn’t have this genetic defect, it is assumed the embryo does not and vice versa. Only those embryos that had the normal cells would then be transferred back into the uterus to allow implantation and pregnancy to occur with a non-afflicted baby. Nowadays, sometimes when a family has a child that has a certain type of leukemia and there is no one in the family with a bone marrow match, couples undergo IVF + PGD to specifically look for an embryo that will carry the bone marrow matching gene and only these embryos are transferred back. Once the baby is born, a small sample of the baby’s bone marrow is taken to save his/her siblings life from leukemia.
Preimplantation Genetic Screening (PGS)
A procedure in which couples simply want to make sure the embryos being transferred back are chromosomally normal. The biopsy can either be performed on a Day Three embryo or on a Day Five blastocyst (embryo). The advantage of doing a day five trophoectoderm biopsy is that multiple cells (not just one) can be biopsied from the area of the blastocyst that is destined to be the placenta. Presently, there are two ways to screen embryos, either through Fluorescent In-Situ Hybridization (FISH) or Comparative Genetic Hybridization (CGH). FISH cannot check all of the chromosomes, so only a few are checked. CGH can check all forty-six (including sex) chromosomes and is becoming commercially available. Both of these procedures only check for the number of chromosomes, which can be great to avoid genetic defects that are associated with these, such as Down’s Syndrome. As several articles are pointing out however, the biopsied cells that are being screened with these two technologies are not necessarily representative of the cell itself. Some “abnormal” cells seem to “self-correct” early on and possibly become normal babies and vice versa. Although CGH is more complete than FISH for checking chromosomes, CGH is in its infancy and requires at present the freezing of the biopsied blastocyst with eventual thawing of the “normal” blastocyst for transfer. At present, PGS remains controversial in the fertility world whether screening provides any benefit since we can’t be sure of the chromosomal findings.
Microarray Chips are presently under scientific investigation in which several hundreds of genes (not just the chromosome number) can be evaluated in each embryo. Lethal and/or debilitating genes found in embryos can primarily be evaluated and only those that do not carry these genes can be transferred, but this technology is still a few years away from being commercially available.
There are still many more technologies being developed, such as finding embryo markers in culture media that by simply checking the media and not manipulating the embryo, we may be able to determine the best embryo. Others are studying flow dynamics to try and mimic the fallopian tube environment for the embryo. Whereas these make sense, we are hopeful that within a few years, we will be able to provide these technologies to you to not only improve pregnancy rates, but to also provide diagnosis when needed.