ABSTRACT
BACKGROUND: Testicular sperm extraction (TESE) is an essential therapeutic tool for the management of male infertility. However, it is an invasive procedure with a success rate up to 50%. To date, no model based on clinical and laboratory parameters is sufficiently powerful to accurately predict the success of sperm retrieval in TESE. OBJECTIVE: The aim of this study is to compare a wide range of predictive models under similar conditions for TESE outcomes in patients with nonobstructive azoospermia (NOA) to identify the correct mathematical approach to apply, most appropriate study size, and relevance of the input biomarkers. METHODS: We analyzed 201 patients who underwent TESE at Tenon Hospital (Assistance Publique-Hôpitaux de Paris, Sorbonne University, Paris), distributed in a retrospective training cohort of 175 patients (January 2012 to April 2021) and a prospective testing cohort (May 2021 to December 2021) of 26 patients. Preoperative data (according to the French standard exploration of male infertility, 16 variables) including urogenital history, hormonal data, genetic data, and TESE outcomes (representing the target variable) were collected. A TESE was considered positive if we obtained sufficient spermatozoa for intracytoplasmic sperm injection. After preprocessing the raw data, 8 machine learning (ML) models were trained and optimized on the retrospective training cohort data set: The hyperparameter tuning was performed by random search. Finally, the prospective testing cohort data set was used for the model evaluation. The metrics used to evaluate and compare the models were the following: sensitivity, specificity, area under the receiver operating characteristic curve (AUC-ROC), and accuracy. The importance of each variable in the model was assessed using the permutation feature importance technique, and the optimal number of patients to include in the study was assessed using the learning curve. RESULTS: The ensemble models, based on decision trees, showed the best performance, especially the random forest model, which yielded the following results: AUC=0.90, sensitivity=100%, and specificity=69.2%. Furthermore, a study size of 120 patients seemed sufficient to properly exploit the preoperative data in the modeling process, since increasing the number of patients beyond 120 during model training did not bring any performance improvement. Furthermore, inhibin B and a history of varicoceles exhibited the highest predictive capacity. CONCLUSIONS: An ML algorithm based on an appropriate approach can predict successful sperm retrieval in men with NOA undergoing TESE, with promising performance. However, although this study is consistent with the first step of this process, a subsequent formal prospective multicentric validation study should be undertaken before any clinical applications. As future work, we consider the use of recent and clinically relevant data sets (including seminal plasma biomarkers, especially noncoding RNAs, as markers of residual spermatogenesis in NOA patients) to improve our results even more.
Subject(s)
Azoospermia , Infertility, Male , Humans , Male , Azoospermia/diagnosis , Azoospermia/therapy , Semen , Retrospective Studies , Prospective Studies , Spermatozoa , AlgorithmsABSTRACT
PURPOSE: To identify patient characteristics associated with successful isolated immature oocyte retrieval (IsO) during ovarian tissue cryopreservation (OTC) and to determine whether they are predictive of the collection of larger numbers of oocytes. METHODS: We retrospectively analyzed all patients undergoing OTC with IsO for fertility preservation over three years of activity at a university hospital. Univariate and multivariate analyses were used to identify the patients with the highest and lowest chances of oocyte recovery, and those with the largest numbers of oocytes. We also analyzed the correlation of IsO with the number of ovarian fragments collected and histological parameters. RESULTS: We analyzed 257 consecutive patients undergoing these procedures, at a median age of 17.1 years [0.3-38.3 years]. Isolated oocytes were obtained from 47.1% of patients, and IsO was more likely in patients with ovulatory cycles (63.0% vs. 38.6%; P≤ .001), without chemotherapy before OTC (61.4% vs. 33.1; P< .001) and with non-malignant diseases other than Turner syndrome (77.5%). Oocyte collection failure rates were highest in patients with Turner syndrome (OR 25.0, 95% CI 3.99-157.0; P< .001) or undergoing chemotherapy with alkylating agents before OTC (OR 37.6, 95% CI 8.36-168.8; P< .001). Prepubescent status (P= .043) and large numbers of ovarian fragments (P< .001) were associated with the retrieval of larger numbers of oocytes. Oocyte recovery was correlated with the presence of follicles in the medulla, but not with follicular density. CONCLUSION: The chances of IsO differ between patients. Identifying patients with the highest chances of success facilitates appropriate resource allocation.
Subject(s)
Fertility Preservation , Turner Syndrome , Female , Humans , Adolescent , Turner Syndrome/pathology , Retrospective Studies , Oocytes , Cryopreservation/methods , Ovary/pathology , Fertility Preservation/methods , Oocyte RetrievalABSTRACT
RESEARCH QUESTION: The reproductive potential of transgender people may be impaired by gender-affirming hormone treatment (GAHT) and is obviously suppressed by gender-affirming surgery involving bilateral orchiectomy. The evolution of medical support for transgender people has made fertility preservation strategies possible. Fertility preservation in transgender women mainly relies on sperm cryopreservation. There are few studies on this subject, and the sample sizes are small, and so it difficult to know whether fertility preservation procedures are feasible and effective in trans women. DESIGN: This retrospective study reports the management of fertility preservation in transgender women referred to the study centre for sperm cryopreservation, and the semen parameters of trans women were compared with those of sperm donors. RESULTS: Ninety-six per cent of transgender women who had not started treatment benefitted from sperm cryopreservation, compared with 80% of those who attempted a therapeutic window and 50% of those receiving hormonal treatment at the time of sperm collection. No major impairment of semen parameters was observed in transgender women who had not started GAHT compared with sperm donors. However, even though the frequency of oligozoospermia was no different, two transgender women presented azoospermia. Some transgender women who had started GAHT could benefit from sperm freezing. None of them were treated with gonadotrophin-releasing hormone (GnRH) analogues. CONCLUSIONS: Parenthood strategies for transgender people have long been ignored, but this is an important issue to consider, especially because medical treatments and surgeries may be undertaken in adolescents or very young adults. Fertility preservation should ideally be offered prior to initiation of GAHT.
Subject(s)
Fertility Preservation , Reproduction/physiology , Transsexualism/physiopathology , Transsexualism/therapy , Adolescent , Adult , Cohort Studies , Cryopreservation , Female , Fertility Preservation/methods , Fertility Preservation/statistics & numerical data , France/epidemiology , Hormone Replacement Therapy/adverse effects , Hormone Replacement Therapy/statistics & numerical data , Humans , Male , Reproduction/drug effects , Reproductive Techniques, Assisted/statistics & numerical data , Retrospective Studies , Semen , Semen Preservation/methods , Semen Preservation/statistics & numerical data , Sex Reassignment Procedures/adverse effects , Sex Reassignment Procedures/statistics & numerical data , Transgender Persons , Transsexualism/epidemiology , Young AdultABSTRACT
Gonadotoxic therapies during childhood may impair future fertility in adult life and fertility preservation techniques should be discussed before starting gonadotoxic therapies. In both sexes, fertility preservation means immature gametes cryopreservation. For girls, ovarian tissue cryopreservation is the only existing option to preserve fertility in prepubertal girls at risk of premature ovarian failure. This promising approach involves the storage of a large number of follicles, which could subsequently be transplanted or cultured to obtain mature oocytes. For boys, spermatogonial stem cells can be cryopreserved and testicular pieces can be stored for future use. For prepubertal boys it is still an experimental procedure. Animal data reveals that healthy offspring were obtained after grafting of frozen spermatogonia and after in vitro maturation.
Subject(s)
Antineoplastic Agents/adverse effects , Fertility Preservation , Adolescent , Antineoplastic Agents/administration & dosage , Child , Cryopreservation , Female , Humans , Male , Neoplasms/drug therapy , Ovary , SpermatidsABSTRACT
Girls who undergo treatment for cancer are at risk of ovarian hormonal dysfunction and subfertility due to the detrimental effects of some chemotherapeutic agents and/or radiotherapy on the gonads. Consequently, fertility-preserving techniques shouldbe discussed before starting gonadotoxic therapy. Ovarian tissue cryopreservation is currently the only option to preserve fertility in prepubertal girls and should be considered if the risk of premature ovarian failure is high. This promising approach involves the storage of a large number of follicles, which may subsequently be transplanted or cultured to obtain mature ovocytes. The results of ovarian tissue cryopreservation in adults are encouraging: at least twenty children have been born after orthotopic autografting of frozen-thawed ovarian cortex. It has been shown twice that transplantedprepubertal ovarian tissue can induce puberty, confirming the functional capacity of frozen-thawed prepubertal ovarian tissue.
Subject(s)
Cryopreservation , Fertility Preservation/methods , Infertility, Female/prevention & control , Ovary/surgery , Replantation , Adolescent , Animals , Antineoplastic Agents/adverse effects , Child , Child, Preschool , Cryopreservation/methods , Female , Humans , In Vitro Oocyte Maturation Techniques , Infant , Infertility, Female/etiology , Neoplasms/therapy , Ovary/drug effects , Ovary/physiology , Ovary/radiation effects , Pregnancy , Primary Ovarian Insufficiency/etiology , Puberty/physiology , Radiotherapy/adverse effects , Transplantation, AutologousABSTRACT
Testicular germ cell tumours (TGCTs) are the most common tumours in young adults of European ancestry. The high heritability and the constantly increased incidence, which has doubled over the last 20 years, strongly suggest that both genetic and environmental factors are likely to shape the TGCT susceptibility. While genome-wide association studies have identified loci associated with TGCT susceptibility, the role played by environmental molecular vectors in TGCT susceptibility remains unclear. Evidence shows that sperm non-coding RNAs provide a good vision of the environmental stresses experienced by men. Here, to determine whether TGCT impacts the abundance of specific non-coding RNAs in sperm, small RNA deep sequencing analysis of sperm of 25 men aged between 19 and 42 years, diagnosed with (n = 16) or without (n = 9) TGCT was performed. The primary analysis showed no statistical significance in the sncRNA population between the TGCT and non-TGCT groups. However, when sperm physiological parameters were considered to look for differentially expressed sncRNA, we evidenced 11 differentially expressed sncRNA between patients and control which allow a clear discrimination between control and TGCT samples after Hierarchical Clustering analysis. Together, these findings indicate that sperm small non-coding RNAs abundance may have the potential for diagnosing men with TGCT. However, specific care should be taken regarding sperm physiological parameters of the TGCT patients. Hence, larger studies are needed to confirm our findings and to determine whether such a signature associates with the risks to develop TGCT.
Subject(s)
Neoplasms, Germ Cell and Embryonal , RNA, Small Untranslated , Testicular Neoplasms , Young Adult , Humans , Male , Adult , Testicular Neoplasms/genetics , Pilot Projects , Genome-Wide Association Study , RNA, Small Untranslated/genetics , Genetic Predisposition to Disease , DNA Methylation , Semen , Neoplasms, Germ Cell and Embryonal/genetics , Spermatozoa/pathologyABSTRACT
BACKGROUND: In 15-49 years-old men, the main cancers are testicular cancer (TC) and lymphomas (L): freezing of ejaculated sperm is primarily used for male fertility preservation (FP) before cancer treatment. Our objective was to analyze the French FP rate in 15-49 years-old men diagnosed with TC or L in 2018. We designed a national descriptive cross-sectional study of sperm banking rate in men with a diagnosis of TC, Hodgkin L (HL) or non-Hodgkin L (NHL). From the French National Cancer Institute (INCa) 2018 data, we extracted the estimated incidence of TC and L in metropolitan France. From the 2018 activity report of CECOS network (Centers for Study and Banking of Eggs and Sperm), we extracted the number of men with TC or L who banked ejaculated sperm. We estimated the proportion of 15-49 years-old men diagnosed with TC or L who banked sperm. RESULTS: Among 15-49 years-old men, INCa estimated 38,048 new cancer diagnoses in metropolitan France in 2018: 2,630 TC and 3,913 L (943 HL and 2,970 NHL). The CECOS network provided data from 26/27 metropolitan centers (96% response rate): 1,079 sperm banking for men with TC, 375 for HL and 211 for NHL. We estimated that the 2018 sperm banking rate in France was 41% for TC, 40% for HL, and 7% for NHL. CONCLUSIONS: To our knowledge, our paper is the first cross-sectional study with multicenter and national data analyzing FP rate in cancer men: it suggests an efficient pathway for men to FP before cancer treatment, compared to previously published studies. Although sperm banking rate in 15-49 years-old men could definitely be improved, further studies should evaluate the information given to patients before gonadotoxic treatments, the factors associated with the absence of sperm banking and whether this lack of referral induces a loss of chance for these men.
RéSUMé: CONTEXTE: Chez les hommes de 15 à 49 ans, les principaux cancers sont le cancer du testicule (CT) et les lymhomes (L): la congélation de spermatozoïdes éjaculés est utilisée en première intention pour leur préservation de fertilité (PF) avant traitement du cancer. Notre objectif était d'analyser le taux de PF chez les hommes de 15 à 49 ans diagnostiqués avec un CT ou un L en 2018 en France. Nous avons réalisé une étude nationale transversale descriptive du taux de congelation de spermatozoïdes chez les hommes âgés de 15 à 49 ans diagnostiqués avec un CT, un L de Hodgkin (LH) ou un L non-Hodgkinien (LNH). A partir des données de l'Institut National du Cancer (INCa) de 2018, nous avons extrait l'incidence estimée de CT et de L en France métropolitaine. A partir des données du bilan d'activité 2018 de la Federation Française des CECOS (Centre d'Etude et de Conservation des Oeufs et du Sperme), nous avons extrait le nombre d'hommes avec un CT ou un L qui ont congelé leurs spermatozoïdes. Nous avons enfin estimé la proportion d'hommes de 15 à 49 ans diagnostiqués avec un CT ou un L qui ont congelé leurs spermatozoïdes. RéSULTATS: Chez les hommes de 15 à 49 ans, l'INCa a estimé en 2018 38 048 nouveaux cas de cancers diagnostiqués en France métropolitaine en 2018: 2 630 CT et 3 913 L (943 LH et 2 970 LNH). Le réseau des CECOS a produit les résultats issus de 26/27 centres métropolitains (taux de réponse de 96%): 1 079 congélations de sperme pour des hommes atteints de CT, 375 pour LH et 211 pour LNH. Nous avons estimé que le taux de congelation de spermatozoïdes de 2018 en France était de 41% pour le CT, 40% pour le LH et 7% pour le LNH. CONCLUSIONS: A notre connaissance, notre travail est la première étude transversale multicentrique de données nationales analysant le taux de PF chez les hommes atteints de cancer: il suggère un parcours patient efficace pour la PF des hommes avant traitement d'un cancer, par rapport aux études précédemment publiées. Bien que le taux de PF chez les hommes puisse certainemen être amélioré, des études futures devraient évaluer l'information donnée aux patients avant traitement gonadotoxique, les facteurs associés à l'absence de PF et si le défaut d'adressage au CECOS induit un perte de chance pour ces hommes. MOTS-CLéS: Chimiothérapie, Radiothérapie, Oncofertiité, Azoospermia, Paternité.
ABSTRACT
FERTILITY PRESERVATION BEFORE OVARIAN MALIGNANCY TREATMENT While most ovarian epithelial malignancies affect postmenopausal women, 12% occur in reproductive age patients. In addition, borderline ovarian tumors and rare non epithelial ovarian tumors are diagnosed in young patients as well. The prognosis of early-stage epithelial tumors, non-epithelial and frontier tumors is good. Increased knowledge in this specific field now allows the development of fertility preservation strategies. They include conservative surgery when applicable, associated with oocyte and / or ovarian tissue cryopreservation. Indications remain limited, and any decision must be validated by a multidisciplinary expert committee. The different strategies depend on specific tumoral or genetic context.
PRÉSERVATION DE LA FERTILITÉ AVANT TRAITEMENT D'UN CANCER DE L'OVAIRE Le cancer épithélial de l'ovaire atteint en majorité les patientes ménopausées. Cependant, 12 % des patientes ont moins de 44 ans. Les tumeurs frontières de l'ovaire et les tumeurs rares non épithéliales sont diagnostiquées plus fréquemment chez les femmes en âge de procréer. Le pronostic des stades précoces et des tumeurs non épithéliales est favorable. Les avancées scientifiques permettent de développer des stratégies de préservation de la fertilité, qui reposent d'abord sur la possibilité d'une chirurgie conservatrice et sur la préservation de gamètes ou de tissus germinaux. Les indications restent néanmoins limitées, et toute décision doit être discutée en réunion de concertation pluridisciplinaire (RCP) de recours. Les différentes stratégies dépendent du contexte tumoral ou génétique.
Subject(s)
Fertility Preservation , Ovarian Neoplasms , Cryopreservation , Female , Humans , Oocytes/pathology , Ovarian Neoplasms/pathology , Ovarian Neoplasms/surgeryABSTRACT
Advances in the oncology field have led to improved survival rates. Consequently, quality of life after remission is anticipated, which includes the possibility to conceive children. Since cancer treatments are potentially gonadotoxic, fertility preservation must be proposed. Male fertility preservation is mainly based on ejaculated sperm cryopreservation. When this is not possible, testicular sperm extraction (TESE) may be planned. To identify situations in which TESE has been beneficial, a systematic review was conducted. The search was carried out on the PubMed, Scopus, Google Scholar, and CISMeF databases from 1 January 2000 to 19 March 2020. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) recommendations were followed in selecting items of interest. Thirty-four articles were included in the systematic review, including 15 articles on oncological testicular sperm extraction (oncoTESE), 18 articles on postgonadotoxic treatment TESE and 1 article on both oncoTESE and postgonadotoxic treatment TESE. Testicular sperm freezing was possible for 42.9% to 57.7% of patients before gonadotoxic treatment and for 32.4% to 75.5% of patients after gonadotoxic treatment, depending on the type of malignant disease. Although no formal conclusion could be drawn about the chances to obtain sperm in specific situations, our results suggest that TESE can be proposed before and after gonadotoxic treatment. Before treatment, TESE is more often proposed for men with testicular cancer presenting with azoospermia since TESE can be performed simultaneously with tumor removal or orchiectomy. After chemotherapy, TESE may be planned if the patient presents with persistent azoospermia.
Subject(s)
Azoospermia , Testicular Neoplasms , Child , Humans , Male , Azoospermia/etiology , Azoospermia/therapy , Testicular Neoplasms/therapy , Quality of Life , Spermatozoa , Testis , Syndrome , Sperm Retrieval , Retrospective StudiesABSTRACT
The aim of this cross-sectional study was to determine which antiretroviral drugs (ARVs) are associated with changes in the characteristics of semen and the impact of these ARVs according to their score penetration into the male genital compartment. Data from 144 men infected with HIV-1 enrolled in an Assisted Reproductive Technology program were analyzed retrospectively. A seminal penetration score of ARV was based on the available literature. The nonparametric Kruskal-Wallis test and chi-square test were used. There was no difference on sperm parameters between NRTI, NNRTI, or PI regimen. In patients receiving NRTIs or PIs no differences were observed between antiretrovirals of these classes. However, in patients receiving NNRTIs, nevirapine (n = 22) was associated with a higher percentage of progressively motile spermatozoa (P < 0.0001) versus efavirenz (n = 38) as well as vitality (P = 0.0004). No relationship was observed between semen quality and the penetration score. NRTIs and PIs were not associated with any semen changes. Nevirapine was associated with a better quality of semen versus efavirenz. It would be of interest to validate, improve and test our penetration score in a prospective study.
Subject(s)
Anti-HIV Agents/administration & dosage , Anti-HIV Agents/adverse effects , HIV Infections/drug therapy , Semen/drug effects , Semen/physiology , Adult , Cross-Sectional Studies , HIV Infections/virology , HIV-1/isolation & purification , Humans , Locomotion/drug effects , Male , Retrospective Studies , Spermatozoa/drug effects , Spermatozoa/physiologyABSTRACT
BACKGROUND: Klinefelter syndrome (KS) is the most common cause of genetic male infertility, as most patients present azoospermia. In the testis, a massive decrease in the number of germinal cells is observed and this can begin early in childhood. Thus, it is possible to collect spermatozoa after sperm collection or thanks to testicular sperm extraction (TESE), but the chances finding spermatozoa are decreasing with the age. Sperm collection or TESE should be performed as early as possible. When KS is diagnosed during childhood or teens, fertility preservation could be beneficial. The minimal age for proposing fertility preservation remains controversial and there is no current recommendation about fertility preservation in young men with KS. DESIGN: In this context, we have conducted a systematic review of the results of fertility preservation in young patients with KS to discuss the optimal age range for offering fertility preservation, including or not a TESE. RESULTS: Six articles were included in the systematic review, with patients between 13 and 24 years-old. Except for one, all young men agreed for sperm collection following masturbation. Azoospermia was diagnosed in all patients presenting homogenous KS. One study reported the presence of spermatozoa in the ejaculate of a young man with mosaic KS. Fifty-eight young man for whom ejaculated sperm collection was unsuccessful have benefited from TESE. Testicular spermatozoa were found and frozen in 27 patients out of the 58 (46.5%). The chances of freezing viable testicular sperm between 14 and 23 years of age do not appear to depend on age. CONCLUSION: Fertility preservation should be proposed in young men, but the optimal age for proposing the first sperm collection could be adapted according to the medical context and the psychological maturity of the young man.
Subject(s)
Infertility, Male/prevention & control , Klinefelter Syndrome/complications , Adolescent , Fertility Preservation/methods , Humans , Infertility, Male/etiology , Male , Young AdultSubject(s)
Azoospermia , Hematopoietic Stem Cell Transplantation , Male , Humans , Semen , Spermatozoa , Testis , Sperm Retrieval , Azoospermia/etiology , Azoospermia/therapyABSTRACT
Information about chemo and/or radiotherapy gonadotoxicity and about fertility preservation is essential. Sperm cryopreservation has to be systematically offered before gonadotoxic treatments. Efficiency of ovarian function preservation with GnRH agonists is still debated. A controlled ovarian stimulation is necessary before oocyte or embryo cryopreservation. It is only feasible if the treatment is not urgent and if the tumor is not hormone-sensitive. If the treatment is highly gonadotoxic, an ovarian tissue cryopreservation may be appropriate. It is the only fertility preservation technique feasible for prepubertal girls. It is now possible to preserve the fertility of prepubertal boys by cryopreservation of testicular tissue. It is essential to send patients and/or their parents to a specialized fertility preservation center.
Subject(s)
Fertility Preservation/methods , Neoplasms/drug therapy , Neoplasms/radiotherapy , Adolescent , Adult , Age Factors , Child , Cryopreservation , Embryo, Mammalian , Female , Fertility/drug effects , Fertility/radiation effects , Humans , Male , Ovarian Follicle/drug effects , Ovarian Follicle/radiation effects , Ovary/drug effects , Ovary/radiation effects , Ovum , Sperm Maturation , Spermatogenesis/drug effects , Spermatogenesis/radiation effects , Spermatogonia/transplantation , Testis/transplantation , Young AdultABSTRACT
OBJECTIVE: To determine whether "pregnancy rate (PR) per thawed embryo," accounting for embryo losses, is more relevant than "PR per ET," generally used in the literature for expressing embryo cryopreservation results. DESIGN: Systematic review. SETTING: University teaching hospital. PATIENT(S): None. INTERVENTION(S): Analysis of reports from January 1983 to February 2009 involving thawing of human cryopreserved embryos. Of the 1,275 articles that were initially identified, 102 met the inclusion criteria. MAIN OUTCOME MEASURE(S): Comparisons between PR per ET and PR per thawed embryo, contribution of embryo loss to PR. RESULT(S): Overall PR, expressed per ET and per thawed embryo, was compared according to the different freezing speeds and cryoprotectants used. Statistical analysis revealed significant differences for four comparisons with one approach to expressing results, not identified with the other. All other statistical analyses gave similar results whichever way the results were expressed. The rate of thawed transferred embryos, a measure accounting for embryo losses, is a good prognostic factor for PR. CONCLUSION(S): Statistical analysis accounting for embryo losses can give results different from those published in the literature. Consequently, the clinical PR per thawed embryo may be a more informative measure for accurate analysis of practices.
Subject(s)
Cryopreservation/methods , Embryo, Mammalian , Quality Indicators, Health Care , Cleavage Stage, Ovum/physiology , Cryopreservation/standards , Efficiency , Embryo Transfer/statistics & numerical data , Female , Humans , Models, Biological , Pregnancy , Pregnancy Rate , Research DesignABSTRACT
OBJECTIVE: To evaluate the extent to which transfers of frozen single embryos increase cumulative pregnancy rates. DESIGN: Retrospective analysis. SETTING: IVF unit of a university hospital. PATIENT(S): Patients undergoing IVF cycles that were carried out from 2001 to 2005 (n = 1758). Patients were assigned to three groups according to the number of embryos frozen: group A, no cryopreservation; group B, a single embryo frozen; group C, several embryos frozen. INTERVENTION(S): Analysis of fresh ETs as a function of the number of embryos frozen and comparison outcomes for the thawing of a single embryo between subgroups B* (only one embryo frozen and thawed) and C* (last embryo of the cohort thawed). MAIN OUTCOME MEASURE(S): Implantation and pregnancy rates after fresh ETs and embryo survival and pregnancy rates after the transfer of a single thawed embryo. RESULT(S): The pregnancy rate per fresh ET increased significantly with the number of embryos frozen: 16.2% in group A, 21.4% in group B, and 26.5% in group C. For single thawed embryos, survival was higher in group C* (91.7%) than in group B* (72.6%). The pregnancy rate was also significantly higher in group C* (19.4% vs. 0%). CONCLUSION(S): The freezing of single embryos is of no benefit in cumulative pregnancy rates. ET strategies should therefore be reviewed.