Preimplantation Genetic Diagnosis PGD Ethics
Genetic Testing of Embryos in Laboratories Before Implantation
Nov 2, 2009
PGD testing is not perfect; as often as 1-10% of the time, the diagnosis is incorrect, because only a single cell is analyzed, and every cell may not carry every genetic defect. Up to 50% of embryos have mosaicism, meaning that some cells may develop differently than others. If the different cell is the one analyzed, the results the genetic testing lab comes up with may not be accurate.
IVF and PGD have to be done together; there’s no other way to test an embryo but to grow it in the IVF lab. PGD also raises serious ethical questions and concerns about the use of PGD testing in the future.
Using PGD for Gender Selection
PGD is often used for gender selection, if a family wants only a male or female child, either because they carry a genetic disease that occurs only in males or females, or for personal reasons. Many, but not all, IVF centers refuse to do PGD testing for sex selection alone, because of the ethical questions it raises. Embryos that aren’t the “right” sex are usually discarded, although they could also be donated to another couple.
The ethics of PGD for gender selection are hotly debated, as they should be. The question of where using PGD for “frivolous” reasons will lead is a frightening one. There’s also a chance of damaging normal embryos during the PGD process. Interestingly, PGD testing does not increase success rate in IVF, although the expectation would be that removing problem embryos from being implanted would improve pregnancy rates,according to a study published in the New England Journal of Medicine.
An alternative to PGD for gender selection is microsort, where sperm are sorted in the lab. Microsort had a success rate of 91% for couples trying for a girl and 76% for those looking for a boy. Microsort can be used without IVF for couples doing into uterine insemination, or can be used with IVF and ICSI (intracytoplasmic sperm injection).
PGD Testing for Familial Disease
It’s understandable that a family that carries a devastating disease such as Tay Sachs, cystic fibrosis, or Huntington’s disease would want to eliminate this from future children. But the problems of using PGD in these cases are similar to those for gender selection; the results may not be accurate, and there’s a chance of damaging a normal embryo. Genetic testing laboratories can only test for some genetic abnormalities, not all, so it’s possible an embryo that doesn’t have a test for disease could have another disease. Parents should also consider that the deadly diseases of today may have cures by the time their child needs them.
The Unknowns of PGD Testing
Some studies have shown that embryos with abnormal chromosomes on day three, when the cell is removed for PGD testing, may "self correct” and have normal chromosomes by day five. Obviously, this isn’t always the case, but it could mean that normal embryos are destroyed. The issue of parents potentially selecting for only blond children, or tall children, or even all male children, is not only ethically concerning but potentially dangerous to society, if not problematic just on a moral level.
PGD Testing, Microsort and the Future
PGD is a relatively new, very expensive, not always successful technology that has a number of pitfalls and potentially dangerous implications for the future. Its use should be limited to serious disease, if even that, not parental personal preferences. Microsort is a good alternative for sex selection without destroying embryos for family gender balance.
Sources
New England Journal of Medicine July 5, 2007 "In Vitro Fertilization with Preimplantation Genetic Screening," Mastenbroek s et al
Preimplantation Genetic Diagnosis Dayal M Zarek S 11 Nov2008
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