As antineoplastic treatments have become more successful, an increasing number of women with cancer survive to endure the long-term consequences of chemotherapy. One of the most important of these consequences in young females is premature ovarian failure and infertility. Owing to increasing survival rates, many of these young women are seeking methods to preserve their fertility. Currently, embryo/oocyte cryopreservation obtained after controlled ovarian stimulation appears to provide the best fertility preservation option. However, patients may not have enough time to undergo ovarian stimulation prior to chemotherapy and/or have contraindications to exogenous gonadotropin administration owing to estrogen-dependant tumors. In vitro maturation of oocytes is an attractive alternative for fertility preservation in cancer patients because it does not require ovarian stimulation and it can be performed at any time of the menstrual cycle. In addition, this technique can be combined with ovarian tissue cryobanking. In this review, we discuss the position of in vitro maturation of oocytes in the fertility preservation strategy in young women.

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Study question Are perinatal outcomes different in pregnancies resulting from frozen embryo transfers (FET), fresh embryo transfers (IVF-ET), ovulation induction (OI) cycles and spontaneous pregnancies (SP)? Summary answer Assisted reproduction techniques (ART) pregnancies are associated with differences in perinatal outcomes when compared to SP, even when different socioeconomic scenarios were considered. What is known already Earlier reviews have suggested that IVF-ET pregnancies are associated with higher gestational risks. However, there have been recent advances in the way ART is performed and studies show controversy as to whether IVF-ET and FET singletons are associated with higher perinatal risks and which are these risks. The objective of this study was to analyze if there are differences when comparing perinatal outcomes in pregnancies resulting from FET, IVF-ET, OI cycles and SP. Study design, size, duration Retrospective cohort study performed at two medical centers in southern Brazil. Data refers to a period from 2013 to 2022 and was collected from electronic records. Participants/materials, setting, methods Data from 6705 singleton pregnancies, divided into four groups: G1, FET (n = 54), G2, IVF-ET (n = 471), G3, OI (n = 121) and G4, SP (n = 6059). Sample included patients from a private reproductive medicine center (G1,G2,G3) and public health hospital (G4) in Brazil. Variables regarding neonatal outcomes were compared between groups and were expressed as mean±SD/median[IIQ] or n(%). Anova and Kruskal-Wallis tests were applied, considering p < 0.05. Main results and the role of chance Comparing G1 vs. G2 vs. G3 vs. G4, the following results found, respectively, mean±DP: maternal age (35.8±5.2 vs. 35.0±3.7 vs. 33.3±3.6 vs. 26.1±6.8, p < 0.001); newborn's weight, kg (3364.7±553.4 vs. 3115.6±565.9 vs. 3195.9±506.3 vs. 3165.1±651.5, p = 0.043); and length, cm (48.6±2.4 vs. 48.1±2.7 vs. 48.2±2.8 vs. 50.4±1.1, p = 0.971); median[IIQ]: gestational age, weeks.days (39[33-41.3] vs. 38.5[22-41] vs. 39[28-41.5] vs. 39 [25-46], p = 0.809); n%: prematurity (11.3 vs. 13.8 vs. 9.8 vs. 8.9, p = 0.006); Apgar 5thmin≥7 (100 vs. 98.4 vs. 99.1 vs. 96.4, p = 0.020); macrosomia (9.2 vs. 3.1 vs. 3.2 vs. 6.0, p = 0.028); C-section (88.6 vs. 91.0 vs. 85.2 vs. 32.0, p < 0.001). It's important to highlight Brazil's health care differences between public and private services, as public's poor assistance could explain lower Apgar index and C-sections (performed only if obstetric indication). Even so, higher macrosomia and preterm rates were found after ART. Limitations, reasons for caution Women who deliver in public hospitals in Brazil usually have a lower socioeconomic status and less access to adequate prenatal care, which could bring bias in some analysis. Also, there is a sample size discrepancy between groups and no data regarding fertile status in the SP patients. Wider implications of the findings The higher prematurity rates and, in FET cases, macrosomia, reinforces previous studies findings on this subject. As infertility is a worldwilde growing condition, comparing SP and ART is essential for better understanding the implantation processes that could improve ART's perinatal results in the future. Trial registration number not applicable