Turner syndrome (TS) is a chromosomal disorder affecting females and is characterized by complete or partial monosomy of one X chromosome. Its estimated incidence is approximately 1 in 2,500 female live births [1,2]. Mosaic karyotypes, most commonly 45,X/46,XX, account for nearly half of TS cases and are associated with marked phenotypic and reproductive heterogeneity [2,3].

Ovarian development in individuals with TS may appear normal during early fetal life; however, substantial germ cell loss begins during mid-gestation and continues throughout childhood and adolescence. This progressive depletion ultimately leads to premature ovarian insufficiency in most affected individuals [4,5]. Women with mosaic TS often retain residual ovarian function, which may permit spontaneous pubertal development and, in some cases, menarche. Even so, the pace and timing of ovarian reserve decline vary considerably and remain difficult to predict, including in women who initially appear to have preserved ovarian activity [4-6].

Given this broad variability in ovarian function, early fertility preservation (FP) counseling is an important consideration for adolescents and young women with TS, particularly those with mosaic karyotypes and evidence of residual ovarian reserve [2,7]. Advances in assisted reproductive technology have made FP strategies, including oocyte cryopreservation, feasible in carefully selected patients. Nonetheless, clinical evidence supporting successful reproductive outcomes using autologous cryopreserved oocytes in women with TS remains limited [7-9].

In 2022, the first live birth following FP using vitrified oocytes was reported in a woman with mosaic TS, providing initial clinical support for oocyte cryopreservation as a potential FP strategy in selected cases [10]. Subsequent reports have described additional successful outcomes, including cases involving women with mosaic TS and polycystic ovarian morphology. Together, these reports further illustrate the heterogeneity of ovarian function in this population and underscore the need for individualized clinical assessment [11,12]. However, most published cases have involved relatively young patients or have been confounded by spontaneous conception before the use of cryopreserved oocytes, and detailed descriptions of embryo chromosomal outcomes have seldom been reported.

Because pregnancies achieved using autologous oocytes from women with TS have been associated with increased risks of chromosomal abnormalities and early pregnancy loss, preimplantation genetic testing for aneuploidy (PGT-A) has been proposed as a possible adjunct for embryo selection in selected cases. In addition, pregnancy in women with TS is associated with increased risks of miscarriage, obstetric complications, and potentially life-threatening cardiovascular events, highlighting the need for thorough preconception evaluation and careful patient selection [2,13]. Data on FP outcomes in women with TS from Asian populations remain especially limited.

Against this background, we report the case of a Korean woman with mosaic TS who underwent oocyte cryopreservation at 34 years of age, with reproductive outcomes derived exclusively from long-term cryopreserved oocytes after 3.5 years of storage. This report provides detailed embryological and chromosomal findings following PGT-A and documents a live birth achieved using vitrified autologous oocytes. By presenting the clinical, embryological, and genetic outcomes of a single well-characterized case, this report adds clinically relevant information to the limited literature on FP in mosaic TS and may help inform counseling and individualized FP strategies in this population.

FP in women with TS remains clinically challenging because follicular depletion begins early in life and is frequently accompanied by chromosomal abnormalities. To date, FP has been attempted in only a limited number of women with mosaic TS, primarily those who retained spontaneous pubertal development and measurable ovarian activity [7,8]. The present case describes reproductive outcomes after oocyte cryopreservation in a woman with mosaic TS who met these favorable clinical criteria. In this case, the vitrified oocytes survived warming, fertilized normally after ICSI, and subsequently developed into blastocysts. These embryological outcomes are comparable to those reported in women without chromosomal abnormalities and are consistent with previous studies suggesting that, with careful patient selection, women with mosaic TS may achieve acceptable embryological outcomes using their own oocytes [6,7,9]. However, these observations should be interpreted cautiously because they are based on a single patient. A notable feature of this case is that pregnancy did not occur spontaneously before embryo transfer. This made it possible to evaluate reproductive outcomes derived exclusively from long-term cryopreserved oocytes without confounding by natural conception. The first report of a live birth following FP using vitrified oocytes in a woman with mosaic TS was published in 2022 [10]. To place the present case in the context of the existing literature, previously reported FP cases in women with mosaic TS are summarized in Table 1 [7,8,10,12,17]. The table presents clinically relevant parameters, including age at FP, AMH levels when available, and karyotype-specific mosaic ratios, thereby improving the clinical interpretability of the summarized cases. This comparison indicates that, although oocyte cryopreservation is feasible, subsequent use for in vitro fertilization and associated live birth outcomes have been rarely reported in this population. In the present case, a relatively high proportion of diploid 46,XX cells (96%) was observed, which may have contributed to the preserved ovarian function and favorable reproductive outcome. These findings should therefore be interpreted cautiously and may not be generalizable to the broader TS population, particularly to patients with a lower proportion of normal cell lines. Compared with previously reported cases, the present case is distinguished by a live birth achieved exclusively through the use of cryopreserved autologous oocytes, without prior spontaneous conception. This finding supports the potential role of oocyte cryopreservation as an FP strategy in carefully selected women with mosaic TS. The previously reported case involved a younger patient with highly favorable ovarian reserve, and its interpretation was limited by the occurrence of spontaneous pregnancy before the use of cryopreserved oocytes. In contrast, the present case demonstrates that assisted reproduction using vitrified oocytes alone can result in a live birth in a woman with mosaic TS in her mid-thirties. Although conclusions regarding age-related outcomes cannot be drawn from a single case, this finding suggests that FP may still be considered beyond early adulthood in selected women who retain ovarian function, which may be relevant during patient counseling. PGT-A identified embryos classified as euploid, aneuploid, and mosaic in this case, reflecting the variability of chromosomal outcomes in embryos derived from women with mosaic TS. Although limited, these findings provide descriptive information that may support individualized embryo selection and treatment planning in this population [11,16]. The decision to perform PGT-A was based on both maternal age and the underlying diagnosis of TS, a condition associated with increased rates of embryonic chromosomal abnormalities and early pregnancy loss. Although current international guidelines do not uniformly recommend routine PGT-A for all patients, its selective use may be considered in high-risk clinical settings, such as in women with sex chromosome abnormalities, to support individualized decision-making regarding embryo transfer. Previous studies have reported higher rates of chromosomal abnormalities and pregnancy loss in pregnancies achieved using autologous oocytes from women with TS, supporting consideration of PGT-A as an adjunctive tool in selected cases [11,16]. The chromosomal findings reported here should be regarded as descriptive rather than representative, but they add limited clinical information to an area in which published data remain sparse. Although the overall clinical benefit of PGT-A remains debated, particularly in younger patients, its selective application in women with TS may help reduce the likelihood of transferring embryos with clinically significant chromosomal abnormalities [12,18]. Another important contribution of this report is the inclusion of data from an Asian population. Most published reports on FP outcomes in TS have originated from Western cohorts, and clinical experience in Asian patients remains limited. Reporting reproductive and embryological outcomes in a Korean patient may therefore contribute to a more comprehensive understanding of possible regional and ethnic variability in FP outcomes. This report has several limitations. It describes a single patient, and the findings cannot be generalized to all women with TS. Uncertainty remains regarding the optimal timing of FP, long-term reproductive outcomes, and the overall benefit of incorporating PGT-A in this population [7,8]. Nevertheless, this case provides additional clinical evidence that oocyte cryopreservation can be a feasible FP option in selected women with mosaic TS who retain ovarian function. These findings underscore the importance of early counseling, careful patient selection, and individualized FP planning.