What you need to know before considering PGD for gender determination
- PGD is a complex procedure:
Preimplantation Genetic Diagnosis (or PGD) requires expertise in genetics, clinical embryology, microsurgery to remove one or more cells from embryos (biopsy), and non-surgical transfer of embryos into the uterus. Needless to say, the laboratory where the chromosome analysis is done must be licensed and its staff must be highly qualified. Each laboratory must establish a technical “error rate” for the tests they perform. This refers to the frequency with which abnormal embryos are diagnosed as normal or normal embryos are diagnosed as abnormal as a result of technical errors. As a patient, you should get as much information as possible regarding the test error rate at the PGD laboratory to which the IVF center refers cases; this rate should be publicly available. Error rates above 5% are considered unacceptable.
- Embryo biopsy may negatively impact pregnancy rates:
A recent study1 shows that the removal of two cells from an embryo on day 3 of development in culture results in lower chances of pregnancy than if one cell were to be removed. But not removing any cells from the embryo for any purpose is probably better than removing one cell! If you have decided to undergo PGD for gender selection you are accepting a small decrease in your chances of conceiving.
- The biopsy effect can be compensated by comprehensive genetic screening:
Although it has been suggested that PGD does not compensate for the trauma caused by the biopsy procedure, this conclusion has been seriously questioned2. Using optimal methods and analyzing at least 9 chromosomes, Reprogenetics has shown that PGD can significantly reduce pregnancy loss in the most vulnerable patients3.
Without PGD, roughly a quarter of IVF pregnancies in women 35-40 years are lost, primarily due to chromosome abnormalities in the embryo. In women 41-42 years this loss increases to 40% of pregnancies. Early pregnancy loss following IVF exacts a high cost on patients both physically and emotionally. It is also financially costly.
Patients should also keep in mind that embryo testing technology has undergone major changes in the last few years and we can now analyze all chromosomes in an embryo using a technique called array CGH. This technique has produced significant improvements in implantation4 rates (up to 60%) with very low error rates (1.8%)5. Our preliminary results at Reprogenetics show that miscarriage rate is <5% following PGD with aCGH.
- The ethics of gender selection:
Gender selection is considered by some to be unethical; it is unlawful in Europe. It is argued that 1) selection can lead to gender discrimination/imbalances or 2) selection inevitably leads to destruction of potentially normal embryos of the unwanted gender. Reprogenetics has studied the use of PGD for gender diagnosis6 and has reached the conclusion that at least in the US the first argument does not apply because the technique is overwhelmingly used for family balancing purposes. However, with respect to the second argument, Reprogenetics encourages couples seeking this procedure to freeze or donate the normal embryos of the unwanted gender provided that they have been screened comprehensively either for 12 chromosomes or all chromosomes.
- If you decide to use PGD for gender selection, the method of choice is one that allows screening for all chromosome abnormalities (aneuploidies) at the same time.
By analyzing 12 chromosomes or all chromosomes with array CGH, you may have a significantly higher chance of conceiving and carrying the pregnancy to term than by analyzing only the sex chromosomes (chromosomes X and Y) and/or fewer than 12 chromosomes. The risk of conceiving a child with Down syndrome and other genetic abnormalities will also be considerably reduced if not entirely avoided.
1 Goessdens et al., Human Reproduction, 2008
2 Munne et al. 2010
3 Munne et al. 2006, Reproductive biomedicine online 12:234-253
4 Schoolcraft et al. 2010
5 Gutierrez-Mateo et al. 2011
6 Colls et al, 2009, Reproductive Biomedicine Online