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0n-going pregnancy after Preimplantation Genetic Diagnosis (PGD) for paternal balanced translocation t(14; 21) (q22; q22.3) using Microarray Comparative Genomic Hybridization

Introduction Results Conclusions

References

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Preimplantation genetic diagnosis (PGD) was introduced in 1990 as an experimental procedure to genetically screen human embryos during an in vitro fertilization (IVF) cycle1, 2. PGD has become an established clinical procedure in assisted reproductive technologies with over 6500 PGD cycles performed worldwide in the last decade, resulting in the birth of well over 1000 healthy babies and a pregnancy rate per transfer of approximately 24%3. Chromosomal analysis of human IVF embryos using fluorescent in situ hybridization (FISH) can now be used for screening of chromosomal aneuploidy in up to 9 – 10 chromosomes4, 5. Studies have shown that fetal chromosomal abnormalities are associated with human implantation failure and pregnancy loss6, 7. Newer technology like comparative genomic hybridization (CGH) allow the enumeration of all 23 pairs of chromosomes8, and combined with the microarray platform, CGH allows for the genome-wide analysis with high resolution and detection of DNA copy number variations9.  A successful on going pregnancy is documented here in a 41 year-old patient whose husband has a balanced chromosomal translocation t(14; 21)(q22; q22.3). The couple had prolonged primary infertility for 14 years. Following intra-cytoplasmic sperm injection (ICSI) and PGD with microarray CGH, two embryos with normal/ balanced chromosomes were transferred in the same cycle, resulting in the current on going pregnancy. 

Carriers of balanced rearrangements rarely show any phenotypic effect but are at risk of producing unbalanced gametes. Chromosomally unbalanced conceptus may miscarry or result in an abnormal live born offspring. PGD is recognized as a reliable and safe reproductive option available to a range of indicated couples including those at risk of passing on an inherited genetic disorder to their offspring and infertile couples with a high chance of producing chromosomally aneuploidy embryos10. Microarray technology has the capability of producing extremely detailed information on one single platform including chromosome copy number and DNA sequence variations11. This modality in our case allowed embryos with normal/ balanced chromosomes to be selected for embryo transfer, leading to a successful pregnancy. 

Materials and MethodsThe patient has a satisfactory antral follicle count and her husband had been diagnosed to carry a chromosome rearrangement [balanced translocation t(14; 21)(q22; q22.3)] albeit a normal seminal analysis. Figure 1:

   

A long down regulation protocol was initiated in August 2011 with subcutaneous buserelin and follitropin- , and 13 oocytes were retrieved. Eleven βoocytes were suitable for ICSI and 7 were fertilized. At day-3 cleavage stage, 6 embryos were selectable for microarray copy number analysis PGD. Blastomere biopsy was done for the 6 embryos, after zona pellucida dissection with a non-contact laser. Samples and reference DNA were amplified and labeled according to manufacturer’s (BlueGnome) specifications. All labeled sample/ reference DNA were applied to microarrays (24Sure+) and co-hybridized overnight. Microarray slides were washed, dried, scanned and analyzed using BlueFuse software version 2.5 (BlueGnome), revealing normal or whole and partial chromosome losses/ gains, including unbalanced inversions and translocations.  Two euploid day-4 embryos were subsequently selected for embryo transfer. A singleton viable pregnancy was achieved and the pregnancy is currently on going. Both mother and fetus are doing well in the antenatal stage and her delivery is due in June 2012. 

Alpha Fertility CentreMalaysia Leong WY, Lee SS, Low SY- Alpha International Fertility Centre, Malaysia