Advanced Services

Cryopreservation and Sperm Preservation

Cryopreservation refers to the freezing of human embryos. Therefore, additional embryos can be preserved. Frozen embryos tend to remain viable for approximately ten years. The embryos are frozen to sub-zero temperatures such as -196 degrees Celsius (the boiling point of liquid nitrogen). Cryopreservation has proved extremely beneficial for couples undergoing ARTs. Cryopreservation has enabled the avoidance of both ovarian induction (OI) and egg retrieval, two stages that are often necessary for several ARTs. As a result, if a patient fails to get pregnant from their first ART, they are able to quickly attempt a second trial. The embryos can be transferred during a normal or artificial cycle, and the patient does not have to undergo ovarian stimulation.

In a patient that has a normal cycle, embryos are transferred 2-3 days after ovulation occurs. An ultrasound is used to confirm the fact that ovulation has taken place. In patients with irregular periods, medications are used to control the menstrual cycle, and develop the endometrial lining. After the endometrium is prepared, Progesterone is administered and the embryos are transferred after three days.

There are a few problems with Cryopreservation. First of all, in some cases the eggs do not always survive the freezing and thawing process. Some embryos are not even suitable for freezing. The average survival rates for frozen embryos are approximately 40-60%. Sometimes, the freezing process results in the development of solution effects, extracellular ice formation, intracellular ice formation, and dehydration. All of these are damaging to the embryos. Recently, vitrification has been introduced to help prevent problems that arise due to ice formation. In vitrification, cryoprotectants are used prior to cooling. This helps lower the freezing point, and increase viscosity of the liquid. As a result, instead of crystallization occurring the liquid becomes an amorphous ice.

A couple that is using Cryopreservation must inform the center about their future intentions regarding the frozen embryos. A separate charge is listed for Cryopreservation.

Sperm can also be frozen and preserved in a similar manner. This is again advantageous to couples, since it allows sperm to be available in case of emergency. For example, situations can arise where a normally fertile man produces a less than adequate sperm sample. In such unforeseen circumstances, sperm that has been frozen can be used. This can prove extremely beneficial if a physician is unable to contact the couple. In many cases the window of opportunity is extremely small, and timing is crucial. Eggs cannot survive a long time after egg retrieval without being fertilized, thus a time delay in insemination of the culture media can have drastic consequences.

Cryopreservation

Blastocyst Transfer

Blastocyst Transfer has become possible due to technological advancements and new culture media. The blastocyst is a characteristic stage in embryonic development. It is often described as a mass of cells surrounding a fluid-filled cavity (blastoceol). This stage is often viewed approximately five days after fertilization. The blastocyst is the stage prior to the hatching process. Therefore, after reaching the blastocyst stage the embryo usually sheds the zona pellucida (outer protien matrix) and then implants in the endometrium.

The main advantage of blastocyst transfer is that it enables the embryologist to observe the embryos for a longer period of time. This often reveals important information on the quality of the embryo and its potential to continue maturation. In addition, blastocyst transfer has helped decrease the incidence of multiple pregnancy. Often only two blastocysts are transferred, and the success of pregnancy is higher or comparable to that of 8-cell stage embryo transfer.

This type of transfer is often recommended for couples that have repeatedly failed to conceive or for those who fear higher order pregnancies.


	Healthy Blastocysts		Blastocyst		Blastocyst Transfer

Laser Assisted Hatching

This is a very recently developed technique used when patients have good grade embryos that have shown repeated failure of implantation. It is also recommended for older patients, such as those above 38 years of age. In order for pregnancy to occur, the embryo must hatch from the zona pellucida (surrounding protein matrix) and implant in the endometrial lining. Consequently, if hatching does not take place, pregnancy will not occur. In laser assisted hatching a laser is used to thin out a portion of the zona pellucida. This procedure helps facilitate hatching and implantation.


	Assisted Hatching Performed in Embryology Lab		Assisted Hatching

Preimplantation Genetic Diagnosis (PGD)

PGD is a procedure used to test embryos for either chromosomal abnormalities or inherited genetic disorders before uterine transfer and the establishment of pregnancy. Therefore, it helps alert couples to the possibility of a problem before the actual implantation of an embryo. PGD is usually used in conjunction with IVF and possibly ZIFT. This diagnosis enables a couple to discover if their child is abnormal before pregnancy, and to avoid having to contemplate the possibility of abortion later during the child-bearing term. PGD can detect approximately 203 inheritable disorders, some of these being cystic fibrosis, Tay-Sachs, beta-thallassemia, sickle-cell anemia, Gaucher's disease, Duchenne muscular dystrophy, spinal muscular dystrophy, myotnoic dystrophy, Lesch-Nyhan syndrome, Hemophilia A and B, fragile X-syndrome, and Kleinfelter's syndrome. Chromosomal abnormalities that can be detected include Down's Syndrome, Turner's Syndrome, known translocations and inversions, and problems in most of the 23 known chromosomes.

PGD is performed by removing a single cell from an embryo. The cell is usually removed from the embryo at the 8-cell stage or later on during development. The biopsied cell is then analyzed for chromosome abnormalities using a panel of chromosomes or for a single gene known to cause an inheritable disorder. Results become available after approximately 24 hours, and then the embryo can be transferred at the blasotcyst stage. The chance of pregnancy after PGD is performed on the embryo is still comparable to cases where the test is not undertaken, therefore it does not seem to negatively affect implantation. There is a 3-8% chance that the test results are erroneous. Therefore, both chorionic villus sampling and amniocentesis are recommended as confirmatory procedures that should be used to ensure normal pregnancy.

PGD should be considered by couples when there is a possibility of passing an inheritable genetic disease, when an individual is aware that they are carriers of a chromosomal abnormality that can be transmitted, when recurrent pregnancy loss has occurred, when IVF has failed repeatedly, and in couples where the woman is over 38 years of age.

PGD is also used for gender selection (choosing the sex of the fetus) by examining the chromosomes (XX for the female and XY for the male) of the embryos that will be transferred to the uterus. It is vitally important in cases where the genetic disorder is linked to gender (for example, Hemophilia, which affects the male offspring).


	Removing a Cell from an 8-Cell Embryo		Dislodging the Cell		Biopsied Cell Removed		PGDVideo (Quicktime)

Chromosomal Karyotyping