In America alone there are 6.1 million couples coping with infertility (ASRM). In vitro fertilization (IVF) is one of the many assisted reproductive technologies used to help infertile couples achieve pregnancy. Since IVF is costly (the average cost is $12, 400. for one cycle), time consuming and a very emotional situation, many couples have a limited amount of opportunities to commit to the procedure and every step should be taken to maximize the chances of a successful healthy pregnancy. Preimplantation genetic diagnosis, or PGD, is a valuable tool for infertility treatment technology and can facilitate in successful IVF cycles.
The IVF procedure involves removal of eggs from the female's ovaries using an ultrasound guided needle and fertilizing them in a laboratory with the male's sperm. After a certain period of incubation, the fertilized embryos are transferred back into the female's uterus. Successful implantation of a healthy embryo into the uterine lining would need to take place for the woman to become pregnant. PGD enables reproductive endocrinologists to test the chromosomal structure of a three-day embryo prior to transfer to the woman's womb (Werlin). The process begins by using DNA probes to biopsy the embryo at the eight-cell stage of development (Figure A). One cell, or blastomere, is removed for analyzing through a small opening in the outer membrane. It is then tested for chromosomal abnormalities. It is only necessary to access one cell from the embryo because in most cases, all the cells will have the same genetic makeup. The remaining embryo is unharmed and placed in an incubator to resume development. If the testing of the blastomere proves the normal chromosomal makeup, the embryo is then transferred to the woman's uterus following regular IVF protocol. Despite the fact that a cell was removed form the embryo, the future fetus is not lacking cells because PGD. The procedure merely delays continued cell division for a few hours, after which the embryo reaches the same number of cells as before and continues its normal development (Fischer).
Implantation failure and miscarriage are the two most common reasons for an unsuccessful IVF cycle. Implantation failure is defined as three or more failed IVF attempts. PGD is being used to improve implantation and decrease the number of miscarriage by testing for a specific chromosomal condition called aneuploidy. Aneuploidy is a situation in which either the egg or sperm has an extra (trisomy) or missing (monosomy) chromosome and is the cause of fifty percent or more pregnancy losses. An embryo with a monosomy will cease to grow before implantation. Only a few carrying a trisomy chromosome would develop to term. Those that are carried to term result in physical and mental defects such as Down's syndrome, Klinefelter Syndrome, trisomy thirteen and trisomy eighteen. By using PGD to transfer only chromosomally normal embryos, the number of...