Study question To investigate the effect of oocyte vitrification on embryo developmental arrest rate accounting for both open and closed systems. Summary answer Open and closed vitrification systems are equally associated with a statistically significant higher embryo developmental arrest rate per MII oocyte vitrified compared to fresh oocytes. What is known already Oocyte cryopreservation has increased in popularity as it enhances women’s reproductive autonomy. Numerous studies have been published evaluating its effectiveness. However, the majority of published evidence commonly include comparisons with the now considered as “outdated” method of slow freezing. Additionally, data principally report on fertilization rates and clinical outcomes. It may be timely and essential to focus strictly on the effect of oocyte vitrification on the developmental potential of the embryo. Further to this, data are lacking on whether employing an open or closed vitrification system may affect the outcome of vitrification. Study design, size, duration A systematic search of the literature was performed in the databases Pubmed/Medline, Embase, and Cochrane Central Library limited to articles published in English up to October 2021. Only studies employing vitrification were included in this meta-analysis. A total of 17 published prospective studies were eligible. The population consists of oocytes that were either vitrified or fresh and subjected to ICSI. A network meta-analysis was performed comparing the type of vitrification system employed and fresh oocytes. Participants/materials, setting, methods The primary outcome measure was developmental arrest rate per MII oocyte vitrified prior to reaching cleavage or blastocyst stage. The secondary outcome measures were fertilization rate per MII oocyte vitrified and developmental arrest rate per 2PN zygote. Further to this, a subgroup analysis was performed according to the stage of developmental arrest. To rank the efficiency between the fresh oocytes and the oocytes vitrified employing the open and closed system, the P-Score was employed. Main results and the role of chance The seventeen studies reporting on the effect of oocyte vitrification on embryo developmental arrest per MII oocyte vitrified, presented with high heterogeneity I2=81%. Vitrified oocytes employing either the open or closed vitrification system presented with a statistically higher embryo developmental arrest rate when compared to fresh oocytes (open-systems:RR:1.16; 95%CI:1.07-1.26; closed-systems:RR:1.19 95%CI:1.06-1.34). No statistically significant difference was observed between the two vitrification systems (open vs closed:RR:0.99;95%CI:0.89-1.10). Subgroup analysis was performed according to the developmental stage of embryo arrest. Similarly to the pooled results, when subgrouping for embryos arresting prior to the cleavage stage, a statistically significant difference on developmental arrest was identified when vitrifying (open-systems:RR:1.44; 95%CI:1.18-1.77; closed-systems:RR:1.51 95%CI:1.12-2.04; 8 studies). However, when subgrouping for embryos arresting prior to the blastocyst stage, no statistically significant difference on developmental arrest was observed when vitrifying (open-systems:RR:1.06; 95%CI:0.98-1.15; closed systems:RR:1.10 95%CI:0.98-1.24; 9 studies). Fertilization rate was significantly lower for vitrified oocytes compared to fresh (open-systems:RR:0.86; 95%CI:0.79-0.93; closed-systems:RR:0.81 95%CI:0.72-0.92), while no statistically significant difference was observed between the two vitrification systems (open vs closed:RR:1.04; 95%CI:0.93-1.16). When comparing developmental arrest rate per 2PN zygote no statistically significant difference was detected between vitrification versus fresh (open-systems:RR:1.01; 95%CI:0.87-1.17; closed-systems:RR:0.98 95%CI:0.78-1.22), or between the two vitrification systems (open vs closed:RR:1.03;95%CI:0.82-1.30). Limitations, reasons for caution The limited number of studies included along with the heterogeneity identified present as limitations of this study. Further studies and especially Randomized Controlled Trials should be conducted in order to evaluate possible effects of oocyte vitrification on embryo development. Wider implications of the findings Oocyte vitrification results to higher developmental arrest rates per oocyte vitrified but not per 2PN zygote. Both vitrification systems perform equally in affecting developmental arrest. The differential expression of miRNAs and cytokinesis-related genes are identified by this systematic review as potential pathways influencing developmental potential following oocyte vitrification. Trial registration number Not applicable

Study question Are Artificial Intelligence (AI) based models effective in robustly predicting in vitro fertilization (IVF) outcome by assessing embryo quality? Summary answer The majority of the AI-based models could provide an accurate prediction regarding live birth, clinical pregnancy, clinical pregnancy with fetal heartbeat and embryo ploidy status. What is known already Precision and consistency in embryo quality evaluation are of paramount importance regarding the outcome of an IVF cycle. Numerous embryo grading and evaluation systems, employing morphological and morphokinetical assessment, have been proposed but without reaching a consensus yet. The main limitation of the aforementioned assessment systems is that they depend on human evaluation, which may be subject to subjectivity and interobserver variation. Thus, automated prediction models may be essential to optimize objectivity and reliability of embryo grading. Artificial neural network models may process microscopy images or time-lapse videos as input to predict the embryos’ potential competency. Study design, size, duration A systematic review and meta-analysis including 18 published studies. The population consists of preimplantation embryos suitable for embryo transfer in IVF/ICSI cycles following employment of an AI-based prediction model. The outcome measures are prediction of live birth, clinical pregnancy, clinical pregnancy with heartbeat and ploidy status. Participants/materials, setting, methods A systematic search of the literature was performed in the databases of Pubmed/Medline, Embase, and Cochrane Central Library limited to articles published in English up to August 2021. The initial search yielded a total of 694 studies with 97 of them being duplicates and other 579 being excluded on the grounds of not fulfilling inclusion criteria. Following full-text screening and citation mining a total of 18 studies were identified to be eligible for inclusion. Main results and the role of chance Four studies reported on prediction of live birth. The sensitivity was 70.6% (95%C.I.: 38.1-90.4%) and specificity was 90.6% (95%C.I.:79.3-96.1%).  The Area Under the Curve (AUC) of the Summary Receiver Operating Characteristics (SROC) curve was 0.905, while the partial AUC (pAUC) was 0.755. Employing the Bayesian approach, the total Observed:Expected ratio (O:E) was 1.12 (95%CI: 0.26–2.37; 95%PI:0.02-6.54). Ten studies reported on prediction of clinical pregnancy. The sensitivity and the specificity were 71% (95%C.I.: 58.1-81.2%) and 62.5% (95%C.I.: 47.4-75.5%) respectively. The AUC was 0.716, while pAUC was 0.693. Moreover, the total O:E ratio was 0.92 (95%CI: 0.61–1.28; 95%PI:0.13-2.43). Eight studies reported on prediction of clinical pregnancy with fetal heartbeat the sensitivity was 75.2% (95%C.I.: 66.8-82%) and the specificity was 55.3% (95%C.I.: 41.2-68.7%). The AUC was 0.722, while the pAUC was 0.774. The O:E ratio was 0.77 (95%CI: 0.54 – 1.05; 95%PI: 0.21-1.62). Four studies reported on the ploidy status of the embryo. The sensitivity and specificity were 59.4% (95%C.I.: 45.0-73.1%) and 79.2% (95%C.I.: 70.1-86.1%) respectively. The AUC was 0.751 and the pAUC was 0.585. The total O:E ratio was 0.86 (95%CI: 0.42 – 1.27; 95%PI: 0.03-1.83). Limitations, reasons for caution The limited number of studies fulfilling inclusion criteria, along with the different designs applied when developing AI models which may lead to increased heterogeneity, stand as limitations. Inclusion of women regardless of their age presents as another limitation, as advanced maternal age has been associated with diminished IVF outcomes. Wider implications of the findings Albeit, our findings support that AI is a highly promising tool in the era of personalized medicine providing precise predictions it does not appear to considerably surpass human prediction capabilities. More studies and more collaborations between the developers are of paramount importance prior to AI becoming the gold standard. Trial registration number Not applicable

Study question What is the level of fertility awareness and attitudes to having children among Greek teenagers and adults? Summary answer Fertility awareness among Greek teenagers and adults is limited with fundamental misconceptions which may be defining attitudes and may impact family planning and reproductive autonomy. What is known already According to the Organization for Economic Co-operation and Development, Greece is among the countries with the highest maternal age at first birth worldwide, while the total fertility rate has decreased alarmingly. The shift towards delayed parenthood is attributed to the lack of education concerning fertility issues and family planning options within the reproductive age population. This leads to dramatic misinterpretations regarding reproductive dynamic and respective choices. This study aimed to present current data and identify knowledge gaps. This will indicate where future initiatives should be focused to improve fertility awareness and education while respecting reproductive autonomy and individualism. Study design, size, duration This was a mixed methods study using an anonymous, online questionnaire. A 41-item questionnaire for adults and a 46–item questionnaire for teenagers were developed originating from a validated questionnaire from a previously published survey conducted in the UK. A total of 780 respondents completed the survey, which was live between the 11th and 26th of May 2022. Participants/materials, setting, methods Participants were adults and teenagers aged 17-45, who had not yet had children but wanted to in the future. Online Survey Software & Tools for WEB design was employed to generate a friendly-format questionnaire for the respondents. The methodology employed was via CAWI (Computer Assisted Web Interviews). The questionnaire addressed demographics, knowledge on fertility matters, opinions and attitudes towards childbearing. Respondents were also offered the “prefer not to say”, and “don’t know” options. Main results and the role of chance The ideal age to have the first child differed significantly between men and women (32.33±4.50 vs 30.64±3.94; p < 0.001), as did the ideal age to have competed a family (38.71±5.18 vs 36.97±4.71; p < 0.001). Teenagers preferred to have completed their family at a younger age than the adults (33.82±5.87 vs 37.64±4.96; p < 0.001). The desired children number was 2.30±0.7 for men, 2.37±0.71 for women and 2.38±0.7 for teenagers. One third overestimated dramatically the start of fertility decline identifying it as age 46. Over 50% of men and teenagers were not aware of the timing of a women’s fertile window. Women seemed to be more informed on fertility and choose the physician as the educational resource (69%, 261/392), while men were mainly informed from their partners, and choose internet as the educational resource (67%,163/244). Women appeared more concerned with their fertility (191/392 vs 64/244) and felt more pressure to have children compared to men (135/392 vs 54/244; p = 0.02) mainly by their family. Interestingly, relating to reasons that my affected the decision to have children, the most common response for women was “I am not financially ready” (45%, 175/392), compared to men’s “I am ready to have children now” (39%, 96/244). Limitations, reasons for caution The fact that more women than men were included in the teenagers’ group posed a limitation. This study portrays knowledge and attitudes of a population of reproductive age that wants to have children, and hence cannot reflect on knowledge and attitudes on fertility of the general population. Wider implications of the findings Findings identify misinterpretations that may jeopardize family-planning, and lead to unintentional childlessness and age-related infertility. The desired number of children was greater than the actual number reported by OECD. This data calls the scientific community to enable informed reproductive choices by working interdisciplinary towards all-inclusively educating the general population. Trial registration number Not applicable