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Competing Interests: Declaration of conflicting interestsThe authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Globally, fertility awareness efforts include well-established risk factors for fertility problems. Risks disproportionately affecting women in the Global South, however, are neglected. To address this gap, we conducted a systematic review and meta-analyses of relevant risk factors to examine the association between risk factors and fertility problems. MEDLINE, Embase, Cochrane Library, regional databases and key organizational websites were used. Three authors screened and extracted data independently. Studies assessing exposure to risk (clinical, community-based samples) were included, and studies without control groups were excluded. Outcome of interest was fertility problems, e.g. inability to achieve pregnancy, live birth, neonatal death depending on study. The Newcastle-Ottawa Scale was used to assess study quality. A total of 3843 studies were identified, and 62 were included (58 in meta-analyses; n = 111,977). Results revealed the following: a ninefold risk of inability to become pregnant in genital tuberculosis (OR 8.91, 95% CI 1.89 to 42.12); an almost threefold risk in human immunodeficiency virus (OR 2.93, 95% CI 1.95 to 4.42) and bacterial vaginosis (OR 2.81, 95% CI 1.85 to 4.27); a twofold risk of tubal-factor infertility in female genital mutilation/cutting-Type II/III (OR 2.06, 95% CI 1.03 to 4.15); and postnatal mortality in consanguinity (stillbirth, OR 1.28, 95% CI 1.04 to 1.57; neonatal death, OR 1.57, 95% CI 1.22 to 2.02). It seems that risk factors affected reproductive processes through multiple pathways. Health promotion encompassing relevant health indicators could enhance prevention and early detection of fertility problems in the Global South and disproportionately affected populations. The multifactorial risk profile reinforces the need to place fertility within global health initiatives., (Copyright © 2023 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Research Question: What is the optimal number of oocytes retrieved at which maximum live birth rate is observed after fresh autologous assisted reproductive technology (ART) cycles for women of different ages?, Design: Retrospective cohort study of all fresh autologous ART aspiration cycles (n = 256,643) undertaken in Australia and New Zealand between 2009 and 2015. Primary outcome measure was live birth rate (LBR) (delivery of at least one liveborn baby at 20 weeks' gestation or over per fresh aspiration cycle). Cycles were grouped according to female age (<30, 30-34, 35-49, 40-44 and ≥45 years) and ovarian response (one to three, four to nine, 10-14, 15-19, 20-25 and ≥25 oocytes). Secondary outcome was incidence of ovarian hyperstimulation syndrome (OHSS) requiring hospitalization., Results: At different oocyte yields, LBR per fresh aspiration cycle peaked and then declined at, depending on female age: <30 years: six to 11 oocytes (LBR 31-34%); 30-34 years: 11-16 oocytes (LBR 29-30%); 35-39 years: nine to 17 oocytes (LBR 21-24%); and 40-44 years: 15-17 oocytes (LBR 11-12%). The incidence of OHSS increased significantly with the number of oocytes retrieved, from 1.2% with 15 oocytes retrieved to 9.3% with 30 or more oocytes retrieved (P < 0.001)., Conclusion: The optimal number of oocytes at which maximum LBR was observed in a fresh aspiration cycle was highly dependent on age. Because of the observational nature of the results, a cause-effect relationship between the number of oocytes retrieved and LBR should not be assumed; evidence from well-designed randomized control trials is required before clinical advice can be suggested., (Copyright © 2020 Reproductive Healthcare Ltd. Published by Elsevier Ltd. All rights reserved.)

The association between the number of oocytes retrieved and fresh live birth rate (LBR) or cumulative LBR (CLBR), and whether an optimal number of oocytes are retrieved when LBR or CLBR are maximized, are highly relevant clinical questions; however published results are conflicting. A systematic review of all eligible studies (n = 16) published until January 2020 on MEDLINE, Embase, Scopus, CINAHL and Web of Science was conducted. Five studies evaluated only LBR from fresh cycles, five studies evaluated only CLBR from stimulated cycles and six evaluated both. A marked difference was observed between the oocyte yields at which LBR and CLBR were reportedly maximized in the individual studies. On the basis of nine studies, the optimal number of oocytes at which fresh LBR seems to be maximized is proposed to be between 12 and 18 oocytes (15 oocytes was the most common suggestion). On the other hand, CLBR continues to increase with the number of oocytes retrieved. This is the first systematic review on the topic, and it suggests that the retrieval of 12-18 oocytes is associated with maximal fresh LBR, whereas a continuing positive association is present between the number of oocytes retrieved and CLBR., (Copyright © 2020 Reproductive Healthcare Ltd. Published by Elsevier Ltd. All rights reserved.)

Study Question: What is the number of oocytes where the maximum cumulative live birth rate per aspiration (CLBR) is observed during ART in women of different ages?, Summary Answer: The maximum CLBR was observed when around 25 oocytes were retrieved in women between 18-35 years of age, around 9 oocytes in women more than 45 years of age and continued to increase beyond 30 oocytes in women between 36-44 years of age., What Is Known Already: The live birth rate per fresh or frozen/thaw embryo transfer (FET) procedure has traditionally been the main measure of ART success. However, with the introduction of highly efficient embryo cryopreservation methods, CLBR encompassing live delivery outcomes from the fresh and all subsequent FET following a single ovarian stimulation and oocyte collection is increasingly viewed as a more meaningful measure of treatment success. There is evidence suggesting that larger oocyte yields are associated with increased likelihood of cumulative live birth per aspiration. Whether this association is the same across female ages has not yet been properly investigated., Study Design, Size, Duration: This is a large retrospective population-based cohort study using data from the Australian and New Zealand Assisted Reproduction Database (ANZARD). ANZARD contains information from all ART treatment cycles carried out in all fertility centres in Australia and New Zealand. Overall, 221 221 autologous oocyte aspiration cycles carried out between January 2009 to December 2015 were included in the analysis., Participants/materials, Setting, Methods: Cumulative live birth per aspiration was defined as at least one liveborn baby at ≥20 weeks gestation resulting from an ART aspiration cycle, including all fresh and FET resulting from the associated ovarian stimulation, until one live birth occurred or all embryos were used. Cycles where no oocytes were retrieved were excluded from analysis as there is no possibility of live birth. Analyses of data were performed using generalized estimating equations to account for the clustered nature of data (multiple cycles undertaken by a woman). Univariate and multivariable regression analysis was performed to identify and adjust for factors known to independently affect cumulative live birth per aspiration. An interaction term between female age and the number of oocytes retrieved was included to assess whether the age of the women was associated with a different optimal number of oocytes to achieve at least one live birth from an aspiration cycle (i.e. the effect-modifying role of female age). The likelihood of cumulative live birth per aspiration was calculated as odds ratios (ORs) with 95% CI., Main Results and the Role of Chance: The median number of oocytes retrieved was 7 (interquartile range, 4-12) and median age of patients was 36 (interquartile range, 33-40). The overall CLBR was 32.2%. The results from the multivariable regression analysis showedthat the number of oocytes retrieved remained a significant predictor (P < 0.001) of cumulative live birth per aspiration after adjusting for female age, parity and cycle count. Compared to the reference group of 10-14 oocytes retrieved, the adjusted odds for cumulative live birth per aspiration increased with the number of oocytes retrieved: 1-3 oocytes, 0.21 (95% CI, 0.20-0.22); 4-9 oocytes, 0.56 (95% CI, 0.55-0.58); 15-19 oocytes, 1.38 (95% CI, 1.34-1.43); 20-24 oocytes, 1.75 (95% CI, 1.67-1.84); and 2.10 (95% CI, 1.96-2.25) with more than 25 oocytes. After stratifying by female age group, the rate of increase in CLBR per additional oocyte retrieved was lower in the older age groups, indicating that higher oocyte yields were more beneficial in younger women. CLBR of patients in the <30 years and 30-34 years age groups appeared to reach a plateau (with only minimal increase in CLBR per additional oocyte retrieved) after retrieval of 25 oocytes at 73% and 72%, respectively, while CLBR of patients in the 35-39 years and 40-44 years age groups continued to increase with higher oocyte yields, reaching 68% and 40%, respectively, when 30 or more oocytes were retrieved. CLBR of patients aged 45 years and above remained consistently below 5%. Findings suggest that the number of oocytes retrieved where CLBR appears to be maximized is around 25 in women between 18-35 years, more than 30 in women between 36-44 years and around 9 in women 45 years and older. However, results for women aged 45 years and older may not be as robust due to the relatively small sample size available in this age group., Limitations, Reasons for Caution: As with all large retrospective database studies, there are potential confounders that cannot be accounted for. Despite the current study being based on complete ascertainment of ART cycles across two countries, ovarian stimulation protocols, oocyte quality parameters and a number of important patient characteristics are not collected by ANZARD. Additionally, a small number of cycles were available for women over 45 years yielding more than 15 oocytes, making these estimates unreliable., Wider Implications of the Findings: The results from this study demonstrate that the number of oocytes retrieved where the maximum CLBR is observed during ART is dependent on female age. This provides information for clinicians and patients to understand the modifying effect of age on the number of oocytes retrieved and the likelihood of success with ART., Study Funding/competing Interest(s): No external funding was used for this study. The Fertility Society of Australia funds the National Perinatal Epidemiology and Statistics Unit to manage ANZARD and conduct national reporting of ART in Australia and New Zealand. Associate Professor Georgina Chambers (G.C.) is employed by the University of New South Wales (UNSW) and is director of the National Perinatal Epidemiology and Statistics Unit at UNSW. G.C. was also a paid member of the Australian governments Medicare Benefits Scheme taskforce on assisted reproductive technologies in 2017., (© The Author(s) 2019. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)