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Preimplantation genetic diagnosis allows the selection and transfer of unaffected (chromosomally normal) embryos which may result in a higher implantation rate per embryo, a reduction in pregnancy loss, and the birth of a higher number of healthy babies. PGD offers a couple an alternative to agonizing over whether to terminate an affected pregnancy after prenatal diagnosis is made following amniocentesis or Chorionic villa sampling (CVS) at later stages of gestation. Almost all genetically linked diseases that can be diagnosed in the prenatal period by either amniocentesis or CVS can also be detected by PGD. The procedure should reduce the psychological trauma experienced by couples who carry an increased risk for an offspring with a genetic disease. Benefits of PGD may include:
- It has been hypothesized that negative selection of aneuploid embryos would improve implantation rates, because of the correlation between advanced maternal age and chromosomally abnormal embryos. Chromosomally normal embryos have higher chances to develop to term. By replacing only chromosomally normal embryos into the uterus, your chances of miscarriage may decrease, and your chances of becoming pregnant might increase. Twenty-one percent of spontaneous abortions are caused by numerical chromosome abnormalities, and the main risk factor is maternal age. Trisomies increase from 2% in women 25 years old to 19% in women over 40. According to the ASRM- SART data (1998), 52% of IVF stimulation cycles in the USA are carried out in women 35 years or older, demonstrating how IVF patient populations would greatly benefit from the screening of chromosome aneuploidies by FISH. It is important to note that the chance of pregnancy and delivery of a healthy child, however, is reduced in patients over 34 years of age (normally less than 50%) due to problems inherent to the IVF procedure. (Click here for RBA IVF Success Rates)
- PGD will be able to identify most chromosomal abnormalities at risk of developing to term. Currently FISH has been applied to PGD of chromosomal abnormalities in X, Y, 13, 14, 15, 16, 18, 21 and 22. This accounts for 70% of aneuploidies detected in spontaneous abortions.
- It is possible that some information about your own eggs and embryos could be beneficial to you in case of future IVF attempts, or may explain past natural conception or IVF failures.
- Future patients may benefit from information obtained from PGD about the connection between chromosomes, failed development and implantation of embryos.
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