Preimplantation Genetic Testing within the Public Healthcare System in Slovenia.

Preimplantation genetic testing (PGT) is the earliest form of prenatal diagnosis that has become an established procedure for couples at risk of passing a severe genetic disease to their offspring. At UMC Ljubljana, we conducted a retrospective register-based study to present 15 years of PGT service within the public healthcare system in Slovenia. We collected the data of the PGT cycles from 2004 to 2019 and compared clinical outcomes for chromosomal and monogenic diseases using different embryo biopsy and testing approaches. In addition, we assessed the extent to which PGT has become the preferred option compared to classic prenatal diagnostics. We treated 211 couples, 110 with single gene disorder, 88 with structural chromosome rearrangement and 13 for numerical chromosome aberration. There were 375 PGT cycles with oocyte retrieval, while embryo transfer was possible in 263 cases resulting in 78 deliveries and 84 children. Altogether, the clinical pregnancy rate per embryo transfer was 31% in 2004-2016 (blastomere biopsy) and 43% in 2017-19 (blastocyst biopsy), respectively. We assessed that approximately a third of couples would opt for PGT, while the rest preferred natural conception with prenatal diagnosis. Our results show that providing a PGT service within the public healthcare system has become a considerable option in pregnancy planning for couples at risk of transmitting a severe genetic disease to their offspring. In Slovenia, approximately a third of couples would opt for PGT. Although the number of cycles is small, our clinical results are comparable to larger centres.

Possible influence of menstrual cycle on lymphocyte X chromosome mosaicism.

PURPOSE: Estrogens are known to selectively influence cell proliferation. Physiological variations of blood hormone concentration might play a role in regulating the level of X chromosome aneuploidy. In this study we observed the percentages of X aneuploid cells in standard lymphocyte cultures from blood samples obtained in relation to the menstrual cycle, noting whether collection occurred during either the follicular or the luteal phase. METHODS: A study consisting of 28 women with X mosaicism and recurrent pregnancy loss, and 28 age-matched healthy controls. Cytogenetic studies were carried out on peripheral blood samples according to standard procedures. RESULTS: A significant difference in the percentage of X aneuploidy was found in blood samples obtained during different phases of the menstrual cycle. In the case group, the mean value of aneuploid cells in the follicular and luteal phase samples was 10.0 and 6.3 % respectively and in the control group, it was 2.8 and 1.0 % (P < 0.0001). The difference in the case group varied between 0 and 8 % (3.6 ± 2.1 %) and in the control group between 0 and 4 % (1.7 ± 1.1 %). The specificity for detecting true X mosaicism was 0.875. We estimate that the initial diagnosis of X mosaicism could be correct in 68 % of patients with recurrent pregnancy loss. CONCLUSIONS: This observational study establishes that the time of blood sampling in relation to the menstrual cycle can influence lymphocyte X chromosome mosaicism. The results, further proven by additional controlled studies, would have practical implications for genetic counselling and fertility treatment.

Low-level X chromosome mosaicism in women with sporadic premature ovarian failure.

Low-level X chromosome mosaicism and its clinical relevance are still under debate. It could be interpreted as a technical artefact, genuine mosaicism or as being age-related. This study evaluated the contribution of X chromosome mosaicism in phenotypically normal women with sporadic premature ovarian failure (POF). During 1999-2008, 114 patients with POF and 64 age matched controls were karyotyped. Thirteen patients (11.4%) had true X chromosome mosaicism (>10% of aneuploid cells) and 12 had (10.5%) low-level X-mosaicism (between 6-10% of aneuploid cells). The mean age of women with true and low-level mosaicism was 26.0 ± 5.65 years and 35.92 ± 3.87 years, respectively (P < 0.001). In the control group the incidence of cells with an abnormal number of X chromosomes was 1-3%. The results have practical implications for genetic counselling and fertility treatment. To search and confirm the low-level mosaicism, a higher number of metaphases should be analysed or additional fluorescence in-situ hybridization analysis must be performed. Although peripheral blood does not reflect the situation in ovarian tissue well, it is presumed that there are different aetiological causes for true and low-level X chromosome mosaicism. The possible causes and reproductive significance of low-level X chromosome mosaicism are discussed.

Premature ovarian failure with FMR1 premutation, X chromosome mosaicism and blood lymphocyte microchimerism.

Genetic causes of premature ovarian failure (POF) comprise less than one-third of all cases, among them X chromosome abnormalities, mutations and polymorphisms in some genes. The frequency of X-chromosome mosaicism in women with sporadic POF has been found to range between 3 and 10%, whereas the prevalence of POF in carriers of the FMR1 premutation is estimated to range between 13 and 25%. We report two successful pregnancy outcomes after in vitro fertilization-embryo transfer with donated oocytes in a woman with severe POF of a complex genetic origin. Chromosome analysis, fluorescence in situ hybridization on cultured peripheral blood lymphocytes and buccal mucosal cells, and molecular genetic studies, using autosomal, Y-chromosomal polymorphic microsatellite or short tandem repeat markers and CGG repeats in the FMR1 gene, were performed. FMR1 premutation, sex chromosome mosaicism and blood lymphocyte microchimerism were found. Assisted reproduction techniques can be safely used in POF women after a thorough clinical evaluation and genetic counselling.

Primary amenorrhoea in a patient with mosaicism for monosomy X and a derivative X-chromosome.

Primary amenorrhoea is defined as the absence of menstruation in phenotypic women aged 16 years or older, if secondary sexual characteristics are present. X chromosome abnormalities probably comprise about one half of all cases, including Turner syndrome and X chromosome rearrangements. Conventional banding cytogenetic methods might miss the accurate detection of structural chromosome abnormalities. The fluorescence in situ hybridization (FISH) and multicolor FISH techniques are required to interpret specific chromosomal rearrangement. As far as we know, we report the first case with chromosome mosaicism for monosomy X and terminal deletion of Xq26 with duplication of Xp11-->pter. In spite of the fact that a 45,X karyotype was detected in 46% of lymphocytes, she was tall and her secondary sexual characteristics were moderately developed, including breast, pubic and axillary hair stages. Cytogenetic and FISH analyses should be considered for patients presenting primary amenorrhoea even if there are no other clinical features suggestive of chromosome abnormality.

A Down syndrome female infant with partial trisomy of chromosome 21--abnormal nuchal translucency screening test.

We describe a case of 24-year-old mother with abnormal nuchal translucency screening test. Standard G banding of chromosomes showed a normal prenatal karyotype. A Down syndrome female infant with partial duplication of the long arm of chromosome 21 was born resulted from a maternal pericentric inversion of region p1.1 to q22.1 of one of chromosome 21. As far as we know this case reports the first abnormal nuchal translucency screening test result due to partial trisomy of chromosome 21.

Distal trisomy 10q/partial monosomy 14q: an unusual clinical picture.

A case of twin boy with partial trisomy for the distal part of the long arm of chromosome 10 (10q24-->qter) and a concomitant monosomy 14(q32-->qter) is reported. The chromosomal abnormalities resulted from a paternal balanced translocation involving chromosomes 10 and 14. An additional clinical feature was observed, viz. hypoplastic lungs. The proband's phenotype was compared to previously reported patients with partial trisomy 10q or 14q deletion.