PGD (Pre-implantation Genetic Diagnosis)
Pre-implantation genetic diagnosis (PGD) is the ability to screen embryos for specific genetic diseases before they are replaced into the uterus. PGD is primarily used to evaluate known carriers of specific single-gene defects, such as Cystic Fibrosis, or for specific chromosomal abnormalities such as Down's Syndrome, Turner's Syndrome, and specific unbalanced translocations. Transferring "screened embryos" lacking the genetic defect makes it extremely unlikely that the disease could be passed to the child.
Who could benefit from PGD?
Patients at risk for having a child with specific genetic diseases such as those listed above, women older than 38, and women with repeated unexplained pregnancy losses. As stated above, PGD can determine the presence or absence of a certain number of chromosomal disorders, but cannot detect genetic disease nor predict congenital malformation.
Why should a patient consider PGD?
The purpose of PGD is to select for replacement only those embryos believed to be chromosomally normal with the intention of reducing the probability of losing the pregnancy or of carrying a chromosomally abnormal baby to term.
How is PGD performed?
First the patient must undergo a cycle of In Vitro Fertilization. Than the pre-embryos obtained have one or two cells, called blastomeres, removed. These cells are than tested for chromosomal abnormalities or for the presence or absence of specific genes, related to the disease of concern. The results are usually available in one to two days. The embryos whose biopsied cells tested to be normal are replaced back into the patients uterus or cryopreserved for later transfer.
Why might PGD benefit women over 38 years old?
As a woman advances in age, her eggs are exposed to an aging process that can lead to chromosomal abnormalities. If the egg has an abnormality with an extra or missing chromosome, the embryo created by that egg would have an extra or missing chromosome. This situation is called aneuploidy. Often the affected embryos will fail to attach to the womb and a pregnancy does not develop or the embryo does attach but miscarriage occurs. Sometimes, the embryo implants and results in the birth of a child with a chromosomal disorder. Some chromosomal disorders that may result include Down’s Syndrome, Turner's Syndrome and Klinefelter's Syndrome. Overall, the risk of aneuploidy is known to increase with maternal age, from 1/385 at 30 to 1/179 at 35, 1/63 at 40 and at the age of 45 the chance of delivering an affected child is 1/19.
For women 35 and over, as much as 35% of pregnancies are miscarried sooner or later. In up to 50% of these cases, a chromosomal abnormality was the reason for the loss. These figures are approximately the same whether the pregnancy is after an IVF procedure or in the general population
For more information on PGD and to schedule an appointment with LifeStart Fertility Center serving greater Los Angeles, please click here to contact us or call us at 818-889-4532.
