Turner syndrome is the most common sex chromosome abnormality in women, with a prevalence of 1/2500. Diagnosis is most common in early childhood or adolescence, but in some cases the syndrome is diagnosed later in life, often related to an infertility work-up. The syndrome has a wide phenotypic spectrum caused by complete or partial absence of an X chromosome. Due to the range of possible abnormalities, including mosaicisms, Turner syndrome does not always present phenotypically and may remain undiagnosed throughout life (1). However, as widely acknowledged, Turner syndrome has a direct negative effect on fertility and most girls diagnosed with Turner syndrome will not undergo spontaneous puberty. It is estimated that approximately 20% of the girls diagnosed with Turner syndrome will spontaneously present initial puberty development, usually breast development, but only 16% of the girls will proceed to menarche (2). The likelihood to present with clinically evident ovarian function is higher in patients with X-chromosome mosaicisms (45X/46XX, 45X/47XXX) than in those having other X-chromosome variants (46X with ring chromosome, 46X with deletion, 46X with isochromosome, or 45X monosomy) (3). Girls with diagnosed Turner syndrome who show signs of ovarian function in childhood and early adolescence most often develop premature ovarian failure around the time of puberty due to rapid atresia of the follicles (4). It is currently recommended to offer reproductive counselling when a Turner diagnosis is confirmed and also to perform a careful cardiac evaluation to exclude comorbidities (5–7).

In women with Turner syndrome cardiac features may contraindicate a future pregnancy. Congenital heart abnormalities and aortic dilatation, which are strongly associated with life-threatening aortic dissection, are more common in Turner patients, where the incidence of maternal and postpartum death has been reported as high as 2% (8–10). If congenital heart abnormalities or acquired aortic dilation is present in women with Turner syndrome, medical assistance to achieve pregnancy is not recommended and other options for parenthood should be advised (5). While data are still heterogeneous, retrospective studies have indicated that with adherence to health care guidelines pregnancies can proceed without increase in cardiovascular complications (8–14).

In Sweden, a National Healthcare Program for patients with Turner diagnosis has been established since 1994, updated subsequently in 2000 and 2013, and is currently known as the Swedish Turner Academy. The program includes recommendations on how girls and women with Turner syndrome should be followed-up throughout life by multidisciplinary teams at the Turner centers established at all university hospitals (15). Since 2013, the program recommends that discussions regarding reproductive options should be initiated soon after diagnosis, and routinely revisited at the time of transition from pediatric to adult healthcare. In all patients that receive a Turner diagnosis irrespective of age, a thorough cardiac evaluation is performed with echocardiography and/or magnetic resonance imaging. This way the cardiovascular status is known before fertility preservation discussions would take place (5).

In order to preserve fertility in patients with Turner syndrome, fertility preservation (FP) should be offered at an early age, before oocyte depletion (6, 16, 17). However, there are no reliable methods to predict the progress of atresia, nor can it be determined if the follicles in pre-pubertal girls are functional or not. This makes routine implementation of FP difficult in patients with Turner syndrome. In most FP programs it is established that if a girl reaches spontaneous menarche, ovarian stimulation and collection of oocytes can be considered (18, 19). In young pre-pubertal girls, it is more difficult to establish an optimal method for FP. A previous Swedish study reporting on ovarian biopsies and ovarian tissue cryopreservation in Turner patients revealed that the probability of identifying ovarian follicles in the biopsies increased if the Turner karyotype showed a mosaicism, if the girls had developed spontaneous puberty, and if the serum Follicle-Stimulating Hormone (FSH) and Anti Müllerian Hormone (AMH) concentrations were normal for age (8). As shown in that study, biopsies were feasible in 47 of 57 girls and follicles were identified in 15 cases. Finding follicles in the ovarian biopsies supports future fertility treatment, e.g., by re-transplantation of the tissue, or, if ovarian function is evident during adolescence or early adulthood, by ovarian stimulation as a complementary option to girls who have previously cryopreserved ovarian tissue (16). A reason to offer ovarian stimulation is the high efficacy of vitrified oocytes, while re-transplantation of ovarian tissue from women and girls with a reduced ovarian reserve at time of cryopreservation is expected to have low success rate.

At Karolinska University Hospital in Stockholm, fertility counselling and FP have been offered to girls and women with the Turner syndrome as part of a clinical study at the Karolinska University Hospital in Stockholm (3), and the center has also been the national reference center for fertility preservation for children. In this study we present treatment outcomes and long-term follow-up of a large cohort of women and girls with Turner syndrome.

The study cohort included all girls and women presenting with Turner syndrome who were referred for fertility preservation counselling at the Karolinska University Hospital, Section of Reproductive Medicine, in Stockholm, Sweden between 1 January 1999 and 31 December 2021. Data on referral, clinical characteristics and utilization of cryopreserved oocytes and tissues have been collected prospectively.

In total, 100 patients with Turner karyotype were counselled for fertility preservation between 1999 and 2021. The majority (59%) of the patients were between 13 and 17 years of age, 27% were prepubertal and 14% were adults. More than half (65%) the patients were referred for fertility counselling between 1999-2005 ( Table 1 ).

Of all patients with Turner karyotype, 39% had monosomal karyotype (45X), 20% had 45X/46XX or 45X/47XXX mosaicism and 36% had an X-chromosome structural anomaly. After 2006 only 20% of the referred girls had a 45X monosomy ( Table 1 ).

This unique cohort provides insight into the fertility choices and options available for young girls with Turner syndrome. In Sweden fertility counselling and fertility preservation is tax-funded and girls and women with Turner syndrome are currently followed up throughout life by multidisciplinary teams at Turner centers established at all university hospitals according to the National Healthcare Program for Turner syndrome. Reproductive options are discussed soon after diagnosis and also at the transition from pediatric to adult healthcare. In presence of any congenital heart or vessel disease pregnancy is not recommended. The current recommendations are that a girl that has a spontaneous start of puberty should be referred for reproductive counselling, and if feasible, based on health and fertility status, stimulated for oocyte cryopreservation before her oocyte reserve is too much reduced by the rapid atresia.

This cohort has been assembled from the fertility preservation unit at Karolinska University Hospital over a period of 22 years. It should be noted that most of the patients who were included before 2006 (57 of 65) underwent ovarian tissue cryopreservation independent of age and pubertal status, as part of a study to evaluate the fertility potential of Turner girls (3). Based on the results from that study, as well as national and international guidelines, most girls included from 2006 and onwards have been referred for fertility preservation only at signs of spontaneous puberty or at expected start of puberty due to a karyotype with mosaicism. When possible, oocyte cryopreservation has been the fertility preservation method of choice, as the method gained recognition as a clinically established method earlier than ovarian tissue cryopreservation, which was still considered experimental until very recently (21).

A majority of the counselled patients underwent fertility preservation, most often through ovarian tissue cryopreservation. Nearly half the patients who underwent a tissue biopsy had observed abnormalities of the ovaries and one in ten patients had no uterus. In total 11 laparoscopies to obtain ovarian biopsies had to be terminated without tissue retrieval. Following the implementation of stricter criteria for referral, all planned biopsies could proceed successfully.

The implementation of more accurate methods of estimating the female ovarian reserve, such as using biochemical markers including serum AMH, and the adherence to updated guidelines drastically reduced the referral rate and only 35 girls and women with Turner syndrome have been counselled between 2006 and 2020. In this later cohort, 74% had spontaneous menarche, ten patients have cryopreserved ovarian tissue, eight patients have undergone successful oocyte cryopreservation, most in late adolescence, and six are planned for follow-up. Only six patients referred after 2006 have been counselled to proceed with other options for family planning due to low hormonal levels or other health issues. This can be compared to the 65 girls counselled between 1999 and 2005 where 71% did not have signs of spontaneous puberty, no ovarian stimulations for oocyte cryopreservation were performed and 97% of patients were planned for ovarian tissue cryopreservation, whereof 15 patients (24%) had observable follicles the in biopsied tissue.

The live birth rate after re-transplantation of cryopreserved ovarian tissue has been estimated to 33-38% in several other patient groups (22–24). However, the potential for pregnancy and live birth is directly correlated with the number of functional primordial follicles available in the biopsied ovarian tissue (25). To date outcome data are limited when ovarian tissue cryopreservation is performed at a very young age (26–28). In patients with Turner syndrome, where rapid atresia is common, the success rate of ovarian tissue re-transplantation is uncertain. While age alone was previously shown as a non-significant factor in predicting the occurrence of follicles in girls above 12 years of age, it should be noted that these results were from a cohort where the patients where all below the age of 20 (3).

Six women in the cohort have given birth following assisted reproduction with donated oocytes. In addition, we have observed five spontaneous pregnancies followed by live births in three women from the cohort (3%), but cannot exclude the possibility of additional undocumented cases. A large French study by Bernard et al. (29) reported a live birth rate of 3.8% (18/480) and an overall 5.6% (27/480) prevalence of spontaneous pregnancies in women with Turner syndrome. Most of these pregnancies occurred in women with mosaic karyotype and only 0.4% (2/480) in women with a non-mosaic (45X) karyotype. Among the three women with children after spontaneous pregnancy in our cohort, one had a monosomy, one an X-chromosome structural anomaly and one a mosaicism. In a recent UK study including 127 pregnancies in 81 women with Turner syndrome (30), 58% (73/127) of pregnancies were spontaneously conceived and all others were conceived using oocyte donation. Among pregnancies in women with monosomy (45X), 29% (9/31) were spontaneously conceived. To our knowledge, there is only one report so far on a successful fertility treatment using cryopreserved oocytes in a woman with Turner syndrome (31).

This study has amassed a large prospective cohort of Turner patients but is limited by the lack of data on follicle status in the biopsies taken after 2006 and incomplete information on spontaneous births. Further, most patients in the cohort are still relatively young. The return rate in the cohort is expected to increase as all patients are still eligible for fertility preservation and some are still prepubertal or adolescent. All patients that have proceeded with fertility treatments can be found among the 42 patients in their thirties. None of the patients that have preserved oocytes have yet reached 30 years of age.

We report two attempts at re-transplantation of ovarian tissue, but as of yet there has been no successful re-transplantation nor any use of the cryopreserved oocytes in our cohort. As the scarcity of promising follow-up data discourages routine use of early ovarian tissue cryopreservation, Turner girls with early onset atresia currently lack promising FP prospects. However, the implementation of the current guidelines with counselling and follow up from onset of puberty has proven useful for identifying Turner girls eligible for fertility preservation.

The datasets presented in this article are not readily available because the datasets could possibly identify the individual participants due to the limited cohort size. Requests to access the datasets should be directed to kenny.rodriguez-wallberg@ki.se.

The studies involving human participants were reviewed and approved by Ethical Review Board of Karolinska University Hospital (Dnr 427/03) and the Regional Ethics Committee of Stockholm (Dnr 2011/1158-31/2, 2014/470-32, 2016/2530-32 and 2018/2255-32). Written informed consent to participate in this study was provided by the participants’ legal guardian/next of kin.

Conceptualization, KR-W. Methodology, KR-W and FL. Formal Analysis, FL. Data Curation, KR-W and FL. Writing – Original Draft Preparation, KR-W, HN and FL. Writing – Review & Editing, KR-W, FS, HN, FL. Funding Acquisition, KR-W. All authors contributed to the article and approved the submitted version.