Introduction:
Preimplantation genetic diagnosis (PGD) for single gene disorders (SGD) has become an alternative method to prevent the birth of an affected child. Also, many couples are now demanding PGD testing for the curative therapy of their affected children suffering from haematopoietic disorders by selecting HLA-compatible healthy embryos. However, several patient specific factors like advanced maternal age and diminished ovarian reserve as well as low chance of finding HLA compatible healthy embryos limit the successful outcome. In this study, we evaluate how the rate of HLA compatible embryos could affect the outcome.
Materials and methods:
This study was conducted at Istanbul Memorial hospital IVF and Genetics department between 2002 and 2006. 35 couples with 42 cycles in SGD group and 61 couples with 99 cycles in HLA±SGD group were evaluated. After using standard controlled ovarian hyperstimulation protocols, ICSI was performed in all cases in order to eliminate the risk of contamination. On third day of embryo development, one or two blastomeres were biopsied to analyze the single gene defect and/or HLA compatibility. Two-round PCR was performed after which minisequencing method was performed to analyze the mutation of interest and STR analysis was performed to determine the HLA haplotypes. Selected embryos were transferred on fourth or fifth day. Mann-Whitney U test, Student t-test and chi-square test were applied to compare the results, where appropriate.
Results:
In comparison of SGD and HLA±SGD group, no significant difference was found between two groups in terms of patient’s age (32.5±4.8 vs. 32.5±5.3), number of mature oocytes (11.02±6.7 vs. 12.1±7.1) and number of biopsied embryos (8.5±4.4 vs. 9.2±5.6) (p<0.05). While 69.7% of the embryos were found to be suitable for transfer in SGD group after mutation analysis, only 11.2% of the embryos were suitable for transfer in HLA±SGD group since HLA compatibility of the embryos was also considered (p<0.001). In SGD group, only 2 out of 42 (4.8%) cycles were cancelled due to the lack of healthy embryos, while in HLA±SGD group, 37 out of 99 (37.4%) cycles were cancelled due to the lack of healthy and HLA compatible embryos (p<0.001). Although the pregnancy rates in transfer cycles of the two groups were similar (47.5% vs. 35.5%, p>0.05), the pregnancy rates were higher in SGD group according to the cycles initiated (45.2% vs. 22.2%, p<0.001). In SGD group, 6 cases ended in early spontaneous miscarriage, 5 singleton pregnancies are ongoing, 10 healthy babies were born (5 singleton, 2 twins, 1 triplet). In HLA±SGD group, 8 cases ended in early spontaneous miscarriage and 1 ectopic pregnancy was diagnosed, 9 pregnancies are ongoing (8 twins, 1 singleton), 5 healthy babies were born (3 singleton, 1 twin). In two cases, hematopoietic stem cells (HSC) obtained from umbilical cord blood were successfully transplanted.
Conclusion:
Advances in IVF and molecular genetics not only improve the outcome in infertility cases but also provide to have a healthy child for the couples who are carriers of a single gene disorder and give an opportunity to have an HLA compatible sibling for the curative therapy of their affected child as well. However, low probability of finding both HLA compatible and healthy embryos for transfer limits the successful clinical outcome. Before starting each cycle for SGD or HLA±SGD, this information should be discussed in detail with the couples. More importantly, these couples, before planning their family, should be informed by physicians about these options.