Cryopreservation of ovarian tissue is likely to become integrated into the treatment of young women, with cancer, who run a risk of losing their fertility. The full functional lifespan of grafts is still being evaluated, because many of the transplanted women have continued to maintain ovarian activity. Some of our first cases have had tissue functioning for ∼ 10 years.

Purpose This study aims to make an account of the children born following transplantation of frozen-thawed ovarian tissue worldwide with specific focus on the perinatal outcome of the children. Furthermore, perinatal outcome of seven deliveries (nine children) from Denmark is reported. Methods PubMed was searched for papers of deliveries resulting from ovarian tissue cryopreservation (OTC). Seven women underwent OTC prior to chemotherapy. Four of these women still had low ovarian function and had tried to conceive. They therefore had tissue autotransplanted to augment their fertility. The other three women had developed premature ovarian insufficiency (POI) after the end of treatment.Results Worldwide, approximately 95 children have been born or will be born in the near future from OTC, including these 9 new children. Information on the perinatal outcome was found on 40 children. The mean gestational age was 39 weeks and the mean birth weight was 3168 g of the singleton pregnancies, which is within internationally recognized normal standards. Furthermore, half the singletons resulted from natural conception and all twins resulted from in vitro fertilization treatment. All seven Danish women became pregnant within 1-3 years after transplantation. They gave birth to nine healthy children. Conclusion The data is reassuring and further suggests that cryopreservation of ovarian tissue is becoming an established fertility preservation method. The seven Danish women reported in this study were all in their early thirties when OTC was performed. Most other reported cases were in the women's twenties. This suggests that the follicular pool in the thirties is large enough and sufficient to sustain fertility.Keywords Fertility preservation . Cryopreservation . Ovarian tissue transplantation . Deliveries IntroductionOvarian tissue cryopreservation (OTC) and transplantation is a relatively new procedure within the area of assisted reproduction technologies (ART). OTC differs from other ART procedures like freezing oocytes or embryos by cryopreserving intact tissue containing small non-growing follicles [1,2]. Although the cryoprotectant media used to freeze ovarian tissue resemble those media used for oocytes and embryos, there are often subtle differences [3,4]. Furthermore, extensive investigations on the effects of cryoprotectants on both human and animal ovarian tissue have not revealed any potential side effects. However, studies in women who had frozen-thawed ovarian tissue transplanted have The original version of this article was revised: There were errors in the Discussion section and the last paragraph should be removed.Capsule The data is reassuring and further suggests that cryopreservation of ovarian tissue is becoming an established fertility preservation method.

IntroductionThe aim of this study is to report the current status of ovarian tissue cryopreservation among alternatives for fertility preservation in the Nordic countries.Material and methodsA questionnaire was sent to 14 Nordic academic reproductive centers with established fertility preservation programs. It covered fertility preservation cases performed up to December 2014, standard procedures for ovarian tissue cryopreservation and oocyte cryopreservation and reproductive outcomes following ovarian tissue transplantation.ResultsAmong the Nordic countries, Denmark and Norway practice ovarian tissue cryopreservation as a clinical treatment (822 and 164 cases, respectively) and their programs are centralized. In Sweden (457 cases), ovarian tissue cryopreservation is practiced at five of six centers and in Finland at all five centers (145 cases). Nearly all considered ovarian tissue cryopreservation to be experimental. In Iceland, embryo cryopreservation is the only option for fertility preservation. Most centers use slow‐freezing methods for ovarian tissue cryopreservation. Most patients selected for ovarian tissue cryopreservation were newly diagnosed with cancer and the tissue was predominantly retrieved laparoscopically by unilateral oophorectomy. Only minor complications were reported. In total, 46 women have undergone ovarian tissue transplantation aiming at recovering fertility, 17 healthy children have been born and several additional pregnancies are currently ongoing. Whenever patients’ clinical condition is permissive, oocyte cryopreservation after hormonal stimulation is preferred for fertility preservation. Between 2012 and 2014, a smaller proportion of females have undergone fertility preservation in the Nordic centers, in comparison to males (1:3).ConclusionsOverall, ovarian tissue cryopreservation was reported to be safe. Slow freezing methods are still preferred. Promising results of recovery of fertility have been reported in Nordic countries that have initiated ovarian tissue transplantation procedures.

Regulation of human ovarian steroidogenesis differs from other species and precise knowledge on how human small antral follicles (hSAF) develop and acquire competence for continued growth and steroid output is still incomplete. The present study has characterized almost 1,000 normal hSAF collected in connection with cryopreservation of ovarian tissue for fertility preservation. The antral follicles (ranging from 3 to 13 mm) were generally aspirated from one ovary surgically removed during the natural cycle, and the follicular fluid (FF) and the granulosa cells (GC) were isolated and snap-frozen. In FF, the following hormones were measured: inhibin-B, inhibin-A, AMH, follistatin, PAPP-A, estradiol, progesterone, testosterone, and androstenedione. In GC, mRNA gene expressions using q-PCR were measured for the following genes: FSHR, AMH, CYP19, and AR. All samples in which one of the abovementioned parameters was measured were included, but typically multiple parameters were measured. Highly significant differences in concentration and follicular content in relation to follicular diameter were found for all measured hormones despite massive variability in-between follicles for any given diameter. The results demonstrate that profound changes take place in the hormonal microenvironment around follicular diameters of 8–11 mm corresponding to when follicular selection occurs. At this point, inhibin-B and inhibin-A showed distinct peaks concomitant with a significant reduction in both AMH protein and mRNA expression. Concentrations of inhibins, androgens, FSHR, and AR were intimately associated, and it is suggested that inhibin-B in combination with PAPP-A and thereby IGF2 activity exerts important paracrine signaling at follicular selection. At the same time upregulation of estradiol synthesis and CYP19 mRNA expression increased steroid output profoundly. Furthermore, the highly significant association between FSHR and AR mRNA gene expression enforces important functions of androgens in follicular development. Collectively, these data reintroduce the understanding of the follicular phase as two parted in which regulation of steroidogenesis differs. The profound changes taking place around follicular selection highlight important paracrine actions of TGF-β family members and IGFs for securing dominance of the selected follicle.