Recurrent Pregnancy Loss (RPL) can be caused by several problems. This page is devoted to the role genetics genetics plays in recurrent pregnancy loss and how PGD (Preimplantation Genetic Diagnosis) is being used as a treatment.
- Overall IVF Success Rate: Some of the studies have a low success rate in treating RPL with invitro fertilization (IVF). When the overall IVF success rates cited in a study are low, then readers must be suspicious of the general “quality of care” and that impact on the study outcome. From a statistical perspective, the number of cases necessary to show a difference between groups goes way up when the difference between groups is small. So, if a center’s overall pregnancy rates are low then they may not be able to detect differences because everyone’s pregnancy rate is reduced and the difference between groups is more difficult to detect.
- PGD Experience: Embryo biopsy is a technically demanding procedure. Like any other procedure, some people have a better technique than others. Some centers have much more experience than others. Variables like, how long the embryo is out of the incubator for the biopsy, how well is the light and temperature controlled, and what is the fertility center’s rate of poorly fixed and prepared cells or how many cells are removed must be taken into account for any accuracy to exist.
- PGD Cell Fixation: Some cell-fixing techniques are more reliable than others
- Non-Diagnostic Result Rate: It has to be asked if the genetics lab uses alternate techniques to determine the genetic result if the initial probes fail. The overall rate of non-diagnostic embryos matters to the outcome because embryos without a genetic diagnosis cannot be selected for transfer.
- Does PGD Decrease Embryo Implantation?: Some experts argue that the implantation rate decreases after PGD. Poma Fertility does not see this. Our implantation rates are equivalent to non-biopsied embryos when controlling for female age.
- How many chromosomes were evaluated? There are 24 possibles chromosomes for testing (23 pairs but the sex chromosomes are X & Y – leading to 23 pairs but 24 chromosomes). Until very recently (perhaps only 2009 and later), we could only test for 12 of the 24 chromosomes.
Two basic genetic mechanisms lead to recurrent miscarriages. One is related to the age of the woman and the other is related to one of the partners having a structurally abnormal chromosome.
- Aneuploidy – an abnormal number of chromosomes
- Structural Chromosome Defects- Structural chromosome defects refer to translocations. A translocation involves a piece of one chromosome getting attached to another chromosome.
Some couples cope well with miscarriages, while others find the experience to be so devastating that they would do almost anything to avoid another loss. This is the a key clinical issue and dilemma. In looking at the statistics, no intervention is really needed for many couples – but they must be willing to be patient and possibly to endure multiple losses.
- RPL is a relatively common disorder (1 in 500 couples)
- Often the cause is unknown – about 50%
- Miscarriages are commonly caused by embryos with abnormal numbers of chromosomes (aneuploidy) – up to 75%
- The long-term prognosis is very good for couples to eventually have a normal pregnancy
- The time to a normal pregnancy is difficult to determine from the medical literature
- Translocations (at least balanced translocations) seem to have a very long time to a successful pregnancy
- PGD seems to be the correct treatment for the genetic basis of the disorder, yet the proof remains elusive
- PGD may well shorten the time to success and decrease the number of miscarriages before a successful pregnancy occurs