Here we give some comments on a session in the upcoming meeting of BCGIP in Nov. 21 – 24 2013 in Shanghai. An international panel will answer that question.

See: http://www.bcgip.com/china/topics.aspx

In preimplantation genetic diagnosis (PGD) we have to differentiate between classical PGD and preimplantation genetic screening (PGS). The indication of the first is hereditary disease in the parents which they want to avoid in their offspring. In Germany e. g. 100 clinical cases per year are expected. From these epidemiological few cases we have to differentiate the indication for the second which is sterility of the parents in the absence of known hereditary disease.

There are over 70.000 IVF / ICSI cycles in Germany per year, the indications for PGS being still unclear. We differentiate five different aims of PGS: increase of pregnancies, decrease of miscarriages, multiples and malformations, and detection of patients who have got aneuploidy in all oocytes or embryos.

We started PGS by polar body biopsy in 1990 in mice, started a preclinical trial by investigation of human fertilization failures in 2000, started a cohort study with fluorescence in situ hybridization (FISH) in 2004, participated in the ESHRE pilot study with array comparative genome hybridization (aCGH) 2009 - 2011 and in the subsequent ESHRE randomised controlled trial (RCT) “ESTEEM” in 2012 - 2014.

Our preclinical and clinical FISH trials found a majority of the oocytes being aneuploid. The first 10 RCTs worldwide could not find an increase of pregnancies. Cohort studies found a decrease of miscarriages (Munné S et al. 1999 ff). The ESHRE aCGH pilot study found three quarters of the oocytes being aneuploid at an average age of 40 years.

Now two RCTs could show an increase of pregnancies by a combination of blastocyst biopsy and aCGH or single nucleotide polymorphism micro-array (aSNP):
- William Schoolcraft et al. http://www.asrm.org/Comprehensive_Chromosomal_Analysis_Shown_to_Improve_IVF_Outcomes/
- Zhihong Yang et al. http://www.molecularcytogenetics.org/content/5/1/24

PGS is applied worldwide. The indications are still not clear. Polar body biopsy and blastocyst biopsy presumably are less traumatic than day three embryo biopsy. Oocyte euploidy seems to be quite low in the human species. The newly applied biopsy techniques in combination with chip technology might bring the long-awaited breakthrough in PGS.