Ovarian tissue grafting: Lessons learnt from our experience with 55 grafts

Utility and Outcomes of Ovarian Tissue Cryopreservation and Transplantation for Gynecologic Cancers: A Systematic Review and Meta-analysis

OBJECTIVE

To evaluate the utility, success, and safety of ovarian tissue cryopreservation and autologous cryopreserved ovarian tissue transplantation for fertility preservation in patients with gynecologic cancers.

DATA SOURCES

A comprehensive search was performed of the MEDLINE, EMBASE, ClinicalTrials.gov, and Cochrane Library databases to identify relevant studies on the utility and outcomes of ovarian tissue cryopreservation and autologous cryopreserved ovarian tissue transplantation for gynecologic cancers from inception until January 23, 2024.

METHODS OF STUDY SELECTION

Two reviewers independently performed the study selection, data extraction, and risk-of-bias assessment, and the results were then reviewed together. Twenty-three studies were included in the current systematic review.

TABULATION, INTEGRATION, AND RESULTS

The resultant data were meta-analyzed to produce a pooled-effect estimate of the utility of ovarian tissue cryopreservation and autologous transplantation in gynecologic cancers as a proportion of all indications. We found that 7.5% and 9.6% of women undergoing ovarian tissue cryopreservation and autologous transplantation, respectively, had gynecologic cancers. In comparison, hematologic malignancies and breast cancer accounted for approximately 66.0% of all indications for these procedures. The return rate for autologous cryopreserved ovarian tissue transplantation in gynecologic cancers (6.0%) was not statistically different from those for other indications. Among women with gynecologic cancer who underwent ovarian stimulation, 27.3% had at least one child, and the ovarian endocrine function was restored in 78.1% of the women after autologous transplantation. The median graft longevity was 32 months, and no graft-site recurrence was reported after autologous transplantation in women with gynecologic cancer.

CONCLUSION

Our results suggest that ovarian tissue cryopreservation and autologous transplantation are feasible options for preserving ovarian function in women with gynecologic cancers, although ovarian tissue cryopreservation is underutilized, and further studies are needed to determine the longer-term outcomes of autologous transplantation.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO, CRD42024498522.

Is Routine Pathology Evaluation of Tissue Removed for Fertility Preservation Necessary?

BACKGROUND

For all fertility preservation (FP) cases at our institution, a biopsy is performed for routine pathology from all gonadal tissue removed. This is not standard at all centers. We reviewed our experience with biopsy for pathological evaluation of ovarian and testicular specimens in FP cases to determine clinical utility.

METHODS

The medical records of individuals who underwent ovarian tissue cryopreservation (OTC) or testicular tissue cryopreservation (TTC) between 2011 and 2023 were retrospectively reviewed under an IRB-approved study at a free-standing tertiary care children's hospital. Patient demographics, diagnosis, operative characteristics, and pathology results were collected.

RESULTS

One-hundred and eighty-three patients underwent OTC, and 134 patients underwent TTC. All patients had their gonadal tissue biopsied for routine pathology. Malignancy was identified in the biopsies of 4 OTC patients (2.2%) and 2 TTC patients (1.5%). Two OTC patients (1.1%) and 2 TTC patients (1.5%) did not have germ cells identified in their biopsy. All OTC and TTC patients and families elected to continue storing tissue for FP after discussion of pathology findings.

CONCLUSIONS

Pathology results provide another data point to help inform patients and their families when making decisions on ovarian or testicular tissue storage and on how tissue may be utilized in the future to restore fertility and/or hormones. There is a low rate of identifying malignancy in gonadal tissue biopsies taken from FP specimens even in patients with known malignancy. However, when malignancy was identified, it could be unexpected and alter the diagnosis and treatment plan significantly for patients.

LEVEL OF EVIDENCE

IV.

First report on successful delivery after retransplantation of vitrified, rapid warmed ovarian tissue in Europe

RESEARCH QUESTION

Cryopreservation of ovarian tissue is one feasible option to preserve female fertility prior to cancer treatment. The slow freezing protocol represents the current standard approach, while vitrification has been suggested as a promising alternative. This paper reports the follow-up and first successful delivery after retransplantation of vitrified, rapid warmed ovarian tissue in Europe.

DESIGN

After the patient received a diagnosis of breast cancer, ovarian tissue was removed laparoscopically and sent via overnight transportation to University Hospital Bonn for vitrification on site. The patient was treated with chemotherapy, leading to ovarian failure. After 2 years, retransplantation of the vitrified, rapid warmed tissue was conducted on site.

RESULTS

Two months after grafting, the patient reported regular menstrual cycles. After 1 further month a clinical pregnancy occurred, which ended in a spontaneous abortion at the 8th week of pregnancy. Six months after grafting, another naturally conceived pregnancy was determined, resulting in the birth of a healthy boy 14 months after retransplantation of the ovarian tissue.

CONCLUSIONS

Complementing the successful deliveries reported by the groups of Suzuki (Japan) and Silber (USA) regarding vitrified tissue, the current results confirm the high potential of this cryopreservation method in a clinical routine setting as an alternative approach to the widespread slow freezing method.

Live birth from ovarian grafted tissue after pelvic radiation for rectal cancer

Objective

To study the management of a woman who returned to conceive after high-dose radiation treatment, with documentation of uterine dosimetry, and the efficacy of ovarian tissue grafted into an irradiated pelvis.

Design

Case report.

Setting

Private and public In Vitro Fertilization units.

Patient

A 26-year-old woman underwent radiation treatment for rectal cancer, with half of the uterus and the fundus being exposed to radiation doses of 50 and 25 Gy, respectively. We report the details of the uterine assessment, determining suitability of conception with her own uterus, pregnancy surveillance, and reproductive outcome.

Interventions

In Vitro Fertilization stimulation grafted ovarian tissue to assist with pregnancy.

Main Outcome Measures

Successful conception and live birth, pregnancy complications and management of high risk pregnancy.

Results

The results of magnetic resonance imaging and pelvic ultrasound showed a small uterus with preserved junctional zone anatomy, and although the endometrium was initially thin after high-dose estrogen administration, endometrial thickness increased with time. Twelve grafted ovarian tissue stimulation cycles led to 4 embryo transfers, the last of which resulted in a live birth. She had 2 cervical cerclage procedures because of cervical shortening and delivered a 3.3-kg healthy female neonate at 38 weeks of gestation via lower-segment cesarean section.

Conclusions

Successful pregnancy is possible from ovarian tissue grafted into an irradiated pelvis, with high-dose uterine exposure. Careful uterine assessment needs to be undertaken to determine suitability of conception attempt with a patient's own uterus, in consultation with the medical team. Further studies are needed to correlate imaging and biopsy findings with reproductive outcomes.

Perinatal outcomes of pregnancies following autologous cryopreserved ovarian tissue transplantation: a systematic review with pooled analysis

OBJECTIVE

This study aimed to synthesize the existing evidence on perinatal outcomes after autologous cryopreserved ovarian tissue transplantation, concurrently identifying key factors influencing these outcomes.

DATA SOURCES

A comprehensive search was performed on MEDLINE, Embase, and Cochrane Library databases to identify relevant studies on the effect of autologous cryopreserved ovarian tissue transplantation on perinatal outcomes from inception to October 22, 2023. Where there was missing information, the authors were contacted for updated data.

STUDY ELIGIBILITY CRITERIA

Observational studies, such as cohort studies, case series, and case reports that reported a live birth after autologous cryopreserved ovarian tissue transplantation, were considered eligible. Studies lacking data on women's demographic characteristics, autologous cryopreserved ovarian tissue transplantation procedure details, or perinatal outcomes were excluded. In addition, cases involving fresh or nonautologous transplantations and those addressing primary ovarian insufficiency were excluded.

METHODS

Two reviewers (M.E. and E.U.) independently performed the study selection, data extraction, and risk of bias assessment, and the results were then reviewed together. The PRISMA guidelines were followed, and the protocol was registered on PROSPERO (CRD42023469296).

RESULTS

This review included 58 studies composed of 122 women with 162 deliveries (154 singletons and 8 twins) after autologous cryopreserved ovarian tissue transplantation, resulting in 170 newborns. Of note, 83.6% of the women had a malignant disease. Moreover, most of these women (51.0%) were exposed to some form of chemotherapy before ovarian tissue cryopreservation. Of the 162 childbirths, 108 (66.7%) were conceived naturally, and 54 (33.3%) were conceived through assisted reproductive techniques. The birthweight of 88.5% of newborns was appropriate for gestational age, whereas 8.3% and 3.1% were small for gestational age and large for gestational age, respectively. The preterm birth rate was 9.4%, with the remaining being term deliveries. Hypertensive disorders of pregnancy were noted in 18.9% of women, including pregnancy-induced hypertension in 7.6%, preeclampsia in 9.4%, and hemolysis, elevated liver enzymes, and low platelet count in 1.9%. The incidences of gestational diabetes mellitus and preterm premature rupture of membranes were 3.8% for each condition. Neonatal anomalies were reported in 3 transplant recipients with 4 newborns: arthrogryposis, congenital cataract, and diaphragmatic hernia in a twin. Finally, among the recipients' characteristics, not receiving chemotherapy before ovarian tissue cryopreservation (odds ratio, 0.23; 95% confidence interval, 0.07-0.72; P=.012) and natural conception (odds ratio, 0.29; 95% confidence interval, 0.09-0.92; P=.035) were associated with a lower perinatal complication rate.

CONCLUSION

On the basis of low certainty evidence from observational studies, perinatal complication rates did not increase after autologous cryopreserved ovarian tissue transplantation compared with the general pregnant population, except for preeclampsia. This could be due to chemotherapy exposure, underlying medical conditions, and the common use of assisted reproductive techniques. Further larger studies are needed to explore the causes of increased preeclampsia incidence in autologous cryopreserved ovarian tissue transplantation pregnancies.

Comparison of orthotopic and heterotopic autologous ovarian tissue transplantation outcomes

OBJECTIVE

To compare the outcomes of orthotopic and heterotopic ovarian tissue transplantation (OTT) techniques.

DESIGN

Mixed prospective-retrospective cohort study.

SETTING

Academic hospital.

PATIENTS

A total of 14 recipients of autologous OTT.

INTERVENTIONS

Of the 14 women, 12 who received orthotopic (n = 6) or heterotopic (n = 6) transplants met the inclusion criteria. All orthotopic transplants and one heterotopic ovarian tissue transplant were performed laparoscopically. Although 5 of the 6 remaining heterotopic transplants were performed subcutaneously under local anesthesia or intravenous sedation, one was performed with robotic assistance. With the exception of one recipient who solely desired restoration of endocrine function, all underwent oocyte retrieval either to cryopreserve oocytes and embryos before the graft function ceased or because they could not otherwise conceive (hysterectomy, radiation damage, and heterotopic transplant).

MAIN OUTCOME MEASURES

Primary outcome measures were graft function and longevity, and the number of embryos generated per retrieval.

RESULTS

The mean age at ovarian tissue harvesting and transplantation was lower in patients with orthotopic vs. heterotopic transplants, although the proportion of transplanted ovarian cortex was lower in heterotopic transplant cases. All grafts restored ovarian endocrine function. Fertilization rates, the number of embryos generated per retrieval, and the mean number of nonarrested embryos were significantly lower in heterotopic OTT. However, time to function and graft longevity were similar between the groups. Although 4 of the 6 women conceived and delivered 7 children among orthotopic ovarian tissue recipients, one recipient had 3 spontaneous live births after heterotopic OTT, presumably because of the induction of function in the remaining menopausal ovary.

CONCLUSIONS

It appears that orthotopic OTT results in higher gamete and embryo quality. However, the endocrine function restoration rate and longevity are similar between the 2 approaches. When feasible, orthotopic OTT should be preferred for those who intend to conceive, although a less invasive heterotopic OTT can be performed for those who primarily desire ovarian endocrine function.

Assessing the impact of transplant site on ovarian tissue transplantation: a single-arm meta-analysis

BACKGROUND

Survival rates of young women undergoing cancer treatment have substantially improved, with a focus on post-treatment quality of life. Ovarian tissue transplantation (OTT) is a viable option to preserve fertility; however, there is no consensus on the optimal transplantation site. Most studies on OTT are nonrandomized controlled trials with limited sample sizes and uncontrolled statistical analyses, leaving the question of which transplant site yields the highest chance of achieving a live birth unanswered.

OBJECTIVE

This meta-analysis aimed to assess the effect of different ovarian transplant sites on postoperative reproductive outcomes.

METHODS

We adhered to the PRISMA Reporting Items for Systematic Reviews and Meta-Analyses recommendations. Systematic searches were conducted in PubMed, Embase, Web of Science, and the Cochrane Library from inception to September 17, 2023. The inclusion criteria were as follows: (1) women who underwent OTT with a desire for future childbirth, and (2) reports of specific transplant sites and corresponding pregnancy outcomes. The exclusion criteria included the inability to isolate or extract relevant outcome data, case reports, non-original or duplicate data, and articles not written in English.

RESULTS

Twelve studies (201 women) were included in the meta-analysis of cumulative live birth rates (CLBR) after OTT. The CLBR, which encompasses both spontaneous pregnancies and those achieved through assisted reproductive technology (ART) following OTT to the ovarian site, was 21% (95% CI: 6-40, I2: 52.81%, random effect). For transplantation to the pelvic site, the live birth rate was 30% (95% CI: 20-40, I2: 0.00%, fixed effect). Combining transplantation to both the pelvic and ovarian sites resulted in a live birth rate of 23% (95% CI: 11-36, I2: 0.00%, fixed effect). Notably, heterotopic OTT yielded a live birth rate of 3% (95% CI: 0-17, I2: 0.00%, fixed effect).

CONCLUSION

Pregnancy outcomes were not significantly different after orthotopic ovarian transplantation, and pregnancy and live birth rates after orthotopic OTT were significantly higher than those after ectopic transplantation.

REGISTRATION NUMBER

INPLASY202390008.

A 16-year bicentric retrospective analysis of ovarian tissue cryopreservation in pediatric units: indications, results, and outcome

Background

Cancer treatments of the last decades improve the survival rate of children and adolescents. However, chemo- and radiotherapy result in gonadal damage, leading to acute ovarian failure and sterility. The preservation of fertility is now an integral part of care of children requiring gonadotoxic treatments. Ovarian tissue cryopreservation (OTC) is an effective fertility preservation option that allows long-term storage of primordial follicles, subsequent transplantation, and restoration of endocrine function and fertility. The efficacy of this technique is well-demonstrated in adults but the data are scarce for pediatric patients. Currently, OTC represents the only possibility of preserving the potential fertility in prepubertal girls.

Procedure

This is a retrospective study of OTC practice of two French centers from January 2004 to May 2020. A total of 72 patients from pediatric units underwent cryopreservation of ovarian tissue before gonadotoxic therapy for malignant or non-malignant diseases. The ovarian cortex was cut into fragments and the number of follicles per square millimeter was evaluated histologically. The long-term follow-up includes survival rate and hormonal and fertility status.

Results

The mean age of patients at OTC was 9.3 years [0.2-17] and 29.2% were postpubertal; 51 had malignant diseases and 21 had non-malignant diseases. The most frequent diagnoses included acute leukemia, hemoglobinopathies, and neuroblastoma. Indication for OTC was stem cell transplantation for 81.9% (n = 59) of the patients. A third of each ovary was collected for 62.5% (n = 45) of the patients, a whole ovary for 33.3% (n = 24) of the patients, and a third of one ovary for 4.2% (n = 3) of the patients. An average of 17 fragments [5-35] per patient was cryoconserved. A correlation was found between the age of the patients and the number of fragments (p < 0.001). More fragments were obtained from partial bilateral harvesting than from whole ovary harvesting (p < 0.05). Histological analysis of ovarian tissue showed a median of 6.0 primordial follicles/mm2 [0.0-106.5] and no malignant cells were identified. A negative correlation was found between age and follicular density (p < 0.001). Median post-harvest follow-up was 92 months [1-188]. A total of 15 girls had died, 11 were still under treatment for their pathology, and 46 were in complete remission. Of all patients, 29 (40.2%) were subjected to a hormonal status evaluation and 26 were diagnosed with premature ovarian insufficiency (POI) (p < 0.001). One patient had undergone thawed ovarian tissue transplantation.

Conclusion

OTC should be proposed to all girls with high risk of developing POI following gonadotoxic therapies in order to give them the possibility of fertility and endocrine restoration.

Current Trends on Bioengineering Approaches for Ovarian Microenvironment Reconstruction

Ovarian tissue has a unique microarchitecture and a complex cellular and molecular dynamics that are essential for follicular survival and development. Due to this great complexity, several factors may lead to ovarian insufficiency, and therefore to systemic metabolic disorders and female infertility. Techniques currently used in the reproductive clinic such as oocyte cryopreservation or even ovarian tissue transplant, although effective, have several limitations, which impair their wide application. In this scenario, mimetic ovarian tissue reconstruction comes as an innovative alternative to develop new methodologies for germ cells preservation and ovarian functions restoration. The ovarian extracellular matrix (ECM) is crucial for oocyte viability maintenance, once it acts actively in folliculogenesis. One of the key components of ovarian bioengineering is biomaterials application that mimics ECM and provides conditions for cell anchorage, proliferation, and differentiation. Therefore, this review aims at describing ovarian tissue engineering approaches and listing the main limitations of current methods for preservation and reestablishment of ovarian fertility. In addition, we describe the main elements that structure this study field, highlighting the main advances and the challenges to overcome to develop innovative methodologies to be applied in reproductive medicine. Impact Statement This review presents the main advances in the application of tissue bioengineering in the ovarian tissue reconstruction to develop innovative solutions for ovarian fertility reestablishment.

Live birth rate after female fertility preservation for cancer or haematopoietic stem cell transplantation: a systematic review and meta-analysis of the three main techniques; embryo, oocyte and ovarian tissue cryopreservation

STUDY QUESTION

What are the chances of achieving a live birth after embryo, oocyte and ovarian tissue cryopreservation (OTC) in female cancer survivors?

SUMMARY ANSWER

The live birth rates (LBRs) following embryo and oocyte cryopreservation are 41% and 32%, respectively, while for IVF and spontaneous LBR after tissue cryopreservation and transplantation, these rates are 21% and 33%, respectively.

WHAT IS KNOWN ALREADY

Currently, fertility preservation (FP) has become a major public health issue as diagnostic and therapeutic progress has made it possible to achieve an 80% survival rate in children, adolescents and young adults with cancer. In the latest ESHRE guidelines, only oocyte and embryo cryopreservation are considered as established options for FP. OTC is still considered to be an innovative method, while it is an acceptable FP technique in the American Society for Reproductive Medicine guidelines. However, given the lack of studies on long-term outcomes after FP, it is still unclear which technique offers the best chance to achieve a live birth.

STUDY DESIGN, SIZE, DURATION

We performed a systematic review and meta-analysis of published controlled studies. Searches were conducted from January 2004 to May 2021 in Medline, Embase and the Cochrane Library using the following search terms: cancer, stem cell transplantation, FP, embryo cryopreservation, oocyte vitrification, OTC and reproductive outcome.

PARTICIPANTS/MATERIALS, SETTING, METHODS

A total of 126 full-text articles were preselected from 1436 references based on the title and abstract and assessed via the Newcastle-Ottawa Quality Assessment Scale. The studies were selected, and their data were extracted by two independent reviewers according to the Cochrane methods. A fixed-effect meta-analysis was performed for outcomes with high heterogeneity.

MAIN RESULTS AND THE ROLE OF CHANCE

Data from 34 studies were used for this meta-analysis. Regarding cryopreserved embryos, the LBR after IVF was 41% (95% CI: 34-48, I2: 0%, fixed effect). Concerning vitrified oocytes, the LBR was 32% (95% CI: 26-39, I2: 0%, fixed effect). Finally, the LBR after IVF and the spontaneous LBR after ovarian tissue transplantation were 21% (95% CI: 15-26, I2: 0%, fixed-effect) and 33% (95% CI: 25-42, I2: 46.1%, random-effect), respectively. For all outcomes, in the sensitivity analyses, the maximum variation in the estimated percentage was 1%.

LIMITATIONS, REASONS FOR CAUTION

The heterogeneity of the literature prevents us from comparing these three techniques. This meta-analysis provides limited data which may help clinicians when counselling patients.

WIDER IMPLICATIONS OF THE FINDINGS

This study highlights the need for long-term follow-up registries to assess return rates, as well as spontaneous pregnancy rates and birth rates after FP.

STUDY FUNDING/COMPETING INTEREST(S)

This work was sponsored by an unrestricted grant from GEDEON RICHTER France. The authors have no competing interests to declare.

REGISTRATION NUMBER

CRD42021264042.

Transplantation of small ovarian tissue fragments using pipelle device is effective: method evaluation and reproductive outcomes

PURPOSE

To assess the feasibility, effectiveness, and reproductive outcomes of transplantation of tiny cryopreserved ovarian pieces through a pipelle cannula during laparoscopic surgery.

METHODS

A retrospective study of patients who underwent ovarian tissue transplantation for fertility restoration between 2004 and 2022. The "pipelle group" had their ovarian cortex cut into tiny pieces of ~ 1-2 mm3 before cryopreservation. The pieces were too small to be handled and transplanted via standard laparoscopic tools. Transplantation was performed using a pipelle cannula during laparoscopic surgery. The "control group" underwent transplants of ovarian cortex pieces 1-2 mm thick, measuring approximately 25-50 mm2 pieces, using standard procedures.

RESULTS

The pipelle group consisted of 4 patients aged 19, 21, 27, and 28 years old at ovarian tissue cryopreservation (OTC). The control group consisted of 14 patients aged 21-30 years old. All pipelle patients restored their endocrine activity, and all of them conceived. FSH levels dropped during the first 3 months following the pipelle transplant. IVF cycle outcomes were similar for both groups. All patients from the pipelle group conceived, resulting in 5 pregnancies and 4 live births (one patient had 2 deliveries, and one additional pregnancy is ongoing), compared to the control group, where 8 patients achieved a total of 20 pregnancies and 18 live births.

CONCLUSION

Pipelle transplantation for tiny cryopreserved ovarian pieces is feasible and effective. This study opens a door for patients who had their ovaries cut into small pieces and may even simplify the procedure in some instances, making ovarian transplant more accessible.

TRIAL REGISTRATION

(#6531-19-SMC) [18/09/2019].

Age-related fertility decline: is there a role for elective ovarian tissue cryopreservation?

Age-related fertility decline (ARFD) is a prevalent concern amongst western cultures due to the increasing age of first-time motherhood. Elective oocyte and embryo cryopreservation remain the most established methods of fertility preservation, providing women the opportunity of reproductive autonomy to preserve their fertility and extend their childbearing years to prevent involuntary childlessness. Whilst ovarian cortex cryopreservation has been used to preserve reproductive potential in women for medical reasons, such as in pre- or peripubertal girls undergoing gonadotoxic chemotherapy, it has not yet been considered in the context of ARFD. As artificial reproductive technology (ART) and surgical methods of fertility preservation continue to evolve, it is a judicious time to review current evidence and consider alternative options for women wishing to delay their fertility. This article critically appraises elective oocyte cryopreservation as an option for women who use it to mitigate the risk of ARFD and introduces the prospect of elective ovarian cortex cryopreservation as an alternative.

A Systematic Review of Ovarian Tissue Transplantation Outcomes by Ovarian Tissue Processing Size for Cryopreservation

Ovarian tissue cryopreservation (OTC) is the only pre-treatment option currently available to preserve fertility for prepubescent girls and patients who cannot undergo ovarian stimulation. Currently, there is no standardized method of processing ovarian tissue for cryopreservation, despite evidence that fragmentation of ovaries may trigger primordial follicle activation. Because fragmentation may influence ovarian transplant function, the purpose of this systematic review was (1) to identify the processing sizes and dimensions of ovarian tissue within sites around the world, and (2) to examine the reported outcomes of ovarian tissue transplantation including, reported duration of hormone restoration, pregnancy, and live birth. A total of 2,252 abstracts were screened against the inclusion criteria. In this systematic review, 103 studies were included for analysis of tissue processing size and 21 studies were included for analysis of ovarian transplantation outcomes. Only studies where ovarian tissue was cryopreserved (via slow freezing or vitrification) and transplanted orthotopically were included in the review. The size of cryopreserved ovarian tissue was categorized based on dimensions into strips, squares, and fragments. Of the 103 studies, 58 fertility preservation sites were identified that processed ovarian tissue into strips (62%), squares (25.8%), or fragments (31%). Ovarian tissue transplantation was performed in 92 participants that had ovarian tissue cryopreserved into strips (n = 51), squares (n = 37), and fragments (n = 4). All participants had ovarian tissue cryopreserved by slow freezing. The pregnancy rate was 81.3%, 45.5%, 66.7% in the strips, squares, fragment groups, respectively. The live birth rate was 56.3%, 18.2%, 66.7% in the strips, squares, fragment groups, respectively. The mean time from ovarian tissue transplantation to ovarian hormone restoration was 3.88 months, 3.56 months, and 3 months in the strips, squares, and fragments groups, respectively. There was no significant difference between the time of ovarian function' restoration and the size of ovarian tissue. Transplantation of ovarian tissue, regardless of its processing dimensions, restores ovarian hormone activity in the participants that were reported in the literature. More detailed information about the tissue processing size and outcomes post-transplant are required to identify a preferred or more successful processing method.

SYSTEMATIC REVIEW REGISTRATION

[https://www.crd.york.ac.uk], identifier [CRD42020189120].