Articles in the field of infertility (2013–2022): a bibliometric analysis

Abstract

To carry out an in-depth analysis of the scientific research on infertility, we performed the first bibliometric analysis focusing on studies involving global literature on infertility during the period 2013–2022. Analysis of 33239 articles in the field of infertility showed a significant increasing trend in the number of publications over the period 2013–2022, with authors mainly from the USA and China. Shanghai Jiao Tong University published the most articles. This study is the first to analyze the global field of infertility (2013–2022) from multiple indicators by bibliometrics, thus providing new insights into the research hotspots and development trends in the field of infertility.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10815-023-02960-3.

Introduction

Infertility is defined as the failure to conceive after 12 months of regular unprotected sexual intercourse [1, 2]. According to a new report published by WHO, around 17.5% of the adult population roughly 1 in 6 worldwide experiences infertility. The most common causes of infertility are ovulation dysfunction, male factor infertility and tubal disease. Unexplained infertility (UEI) is defined as the absence of identifiable causes for the infertility. Around 30–50% of infertile couples have UEI [3]. Both lifestyle and environmental factors such as smoking, obesity and radiation have a negative impact on fertility [4, 5].

Bibliometric analysis is an effective tool to analyze the research trends and a specific field. It can comprehensively investigate the research hotspots and research status in a certain field, and it is a scientific metrological method for descriptive analysis of research [6, 7]. Bibliometric analysis has developed rapidly in the past few decades and has been widely used in many fields and disciplines, such as medicine and biology [8, 9].

In recent years, the number of articles in the field of infertility has increased rapidly. We retrieved and collected the research literature about infertility in the past ten years from Web of Science, and to analyze and visualize the research literature from multiple aspects using CiteSpace and VOS viewer. This paper reveals the research hotspot and development trend in the field of infertility in past ten years in order to provide new insights into the research of infertility. The results of these analyses will help future researchers to quickly grasp the overall research progress in the field.

Materials and methods

Data

The literature data retrieved in this paper are from the Web of Science Core Collection, document types of article or review, TS = infertility and time span of 2013–2022[(TS = (infertility)) AND PY = (2013–2022)]. A total of 33239 articles were finally retrieved for analysis.

Methods

The evaluation indicators used for analysis in this paper include: number of published articles, journals, countries and regions, organizations, authors and keywords. These articles were mainly analyzed by VOSviewer(Nees Jan van Eck and Ludo Waltman, https://www.vosviewer.com/) and the analysis method was association strength. Keywords with the citation bursts were analyzed by CiteSpace (Chaomei Chen, CiteSpace version 5.7.R5: https://citespace.podia.com/) [10, 11]. CiteSpace provides three cluster labeling algorithms, which are latent semantic indexing, the log-likelihood ratio and mutual information [12–14]. The micro-knowledge distribution characteristics were analyzed by authors, journals and disciplines.

Results

Countries and regions

There were 27370 articles and 5869 reviews among the 33239 publications. Figure 1 shows a line graph of the number of published articles over ten years. As shown in the graph, the number of articles in the field of infertility maintained a slow growth trend from 2013 to 2017 and grew at a faster pace from 2017 to 2021, indicating that more and more researchers are devoted to the field of infertility research. There was a big jump in the number of articles in 2017, which indicates that the field of infertility developed rapidly in 2017. However, the smaller increase in the number of articles from 2021 to 2022 may be due to the impact of COVID-19. The top 10 most productive countries and regions are shown in Supplementary Table 1.

Fig. 1.

The number of articles varies by year

The USA was in the leading position in terms of the number of publications, citations and centrality, followed by China and Italy (Fig. 2). This shows that these countries are playing important roles in promoting the development of infertility research.

Fig. 2.

Co-occurrence relations analysis: country. The analysis method was association strength. Circle size indicates the number of documents, color indicates the average published year and thickness of lines indicates the strength of the relationship

Organizations and authors

Through analyzing the characterization of the authors' cooperation network, it identified the core group of authors and social connection among researchers on infertility. The most prolific institution was Shanghai Jiao Tong University (documents n = 466, citations n = 9134), followed by University of Tehran (documents n = 396, citations n = 4537), (see Supplementary Table 2). The co-occurrence relations are shown in Fig. 3a: organizations with a higher number of publications had a closer relationship, which means increased communication and cooperation are conducive to publishing achievement. Ashok Agarwal from the Cleveland Clinic Foundation had the most publications, with 190 documents, suggesting that Ashok Agarwal had a certain influence on the field of infertility (Fig. 3b). Ashok Agarwal has mainly focused on male infertility. The yellow nodes indicate that the average publishing year of organization is 2020. In Fig. 3b, Cao Yunxia (yellow node) may be a potential emerging researcher. Multiple yellow nodes also mean infertility still attract the attention of investigators.

Fig. 3.

Co-occurrence relations analysis: (a) organizations and (b) authors. The analysis method was association strength. Circle size indicates the number of documents, color indicates the average published year and thickness of lines indicates the strength of the relationship

Journals

It is helpful to identify core journals by analyzing the publication sources. The top 10 journals with the largest number of publications are shown in Supplementary Table 4. Fertility and Sterility has the largest number of publications, with 1088 documents and an impact factor of 8.109, followed by Human Reproduction, which has 931 documents and an impact factor of 7.736. Based on the number of publications and the impact factor of journals, Human Reproduction and Fertility and Sterility might be the more influential journals in the field of infertility.

Keywords analysis

A total of 31,790 keywords were extracted, of which 347 appeared more than 100 times. Supplementary Table 5 shows the top 10 keywords co-occurrence terms. “infertility” (4570), “women” (4445), “in-vitro fertilization” (2811), “expression” (2698), “male-infertility” (2197), and “pregnancy” (2040), “oxidative stress” (1990) were core contents of infertility research. Cluster analysis can show the knowledge structure of the research field [15]. As shown in Fig. 4a, we can see the clusters of red, green, yellow, and blue, which respectively represent four different research directions. The main keywords of the red cluster are infertility, women, pregnancy and polycystic ovary synthesis, which are related to female infertility research. The keywords of the yellow cluster focus on the male infertility, which includes male infertility, men, oxidative stress, fertilization, spermatozoa and DNA-damage. While the keywords of the green cluster are related to the molecular mechanism, including expression, gene, cells and activation. The blue cluster mainly includes in-vitro fertilization, pregnancy, outcomes and embryo-transfer, which are related to the treatment of infertility countermeasures. The overlay map (Fig. 4b) shows that pathogenesis, mutations, obesity, stress, depression are emerging fields that were colored yellow. Figure 5 shows the top 25 keywords with the most robust citation bursts. Notably, mesenchymal stem cell, frozen embryo transfer and fertilization in vitro were in burstiness until 2022.

Fig. 4.

Keywords related to infertility research. (a) Network visualization of keywords drawn by VOSviewer. The circle size means the frequency of occurrence; the circle colors mean different clusters; (b) Overlay visualization of keywords drawn by VOSviewer. The circle size means the frequency of occurrence; the circle colors mean the average published year

Fig. 5.

Top 25 keywords with the strongest citation bursts involved in infertility research

Discussion

This study conducted a bibliometric analysis of 33239 articles published in the field of infertility in the last decade. From the perspective of co-occurrence of countries, the USA published the most articles, followed by China. Four of the top 10 organizations are in China and two in USA, indicating that China and USA have been a leader in the field of infertility. From the perspective of co-occurrence relationship of authors, the authors with the largest number of published articles are closely related to other authors, and the top 10 institutions with the highest number of published articles are closely related to each other, which indicates that the cooperation between institutions and authors is more conducive to the in-depth exploration and development of research.

Ashok Agarwal is the most published and cited author in this field. He has long studied in male infertility. Qiao jie and Russ Hauser are also very influential writers whose works are widely cited. The above authors are influential in the field of infertility because they have made outstanding contributions.

Usually, there is a close relation between the impact of a journal and the impact of its articles. Amid the top 10 journals that had the most published papers, Fertility and Sterility exhibited the highest IF (8.109) and the most prolific journal, which is a leading journal in the field of infertility. The journal is sponsored by USA in 1950, which is an international journal for researchers, who treat and investigate problems of infertility and human reproductive disorders.

In bibliometrics, keyword co-occurrence can reflect the hotspot of an academic field and the evolution of new hotspots, and keyword burst can characterize the emerging topics in a discipline [16, 17]. In this study, we attempted objectively to evaluate the hotspots and frontiers of research on infertility by analyzing keyword co-occurrence (Fig. 4a), keyword overlap (Fig. 4b) and keyword burst (Fig. 5).

Keyword analysis showed that the etiology of infertility was the focus of infertility research. As research goes on, emerging topics occurred continuously. The risk factors associated with infertility, such as obesity, depression and stress are also the hotspots and emerging research trends. Weight loss in women has been shown to promote pregnancy, and excess fat accumulation affects ovulation and oocyte growth [18–20]. High BMI not only reduces sperm quality, but also changes the physical and molecular structure of the germ cells in the testes, ultimately affecting the maturation and function of the sperm cells, thus negatively affecting the male reproductive potential [21–23]. There may be a link between stress and reproductive system hormones, such as prolactin, which can affect the reproductive capacity of people of childbearing age. Therefore, the mental state before treatment has a huge and direct impact on the treatment outcome [24, 25].

Keyword with strong bursts could also feature the emerging topics of a field [26]. Among the top 25 keywords with the strongest bursts, mesenchymal stem cell and embryo-transfer are still in the bursting phase. These articles about mesenchymal stem cell represent the latest emerging topics of infertility research, and indicate future potential research directions, such as MSCs on POI treatment, mesenchymal stem cells (MSCs) in the treatment of various types of male infertility.

MSCs are a kind of pluripotent stem cells with differentiation, proliferation and self-renewing ability. The four most prominent mechanisms of action of mesenchymal stem cells in treating infertility are their differentiation biology, secretory capacity, mitochondrial transfer, and immunomodulatory and anti-inflammatory capacity.

Several studies have shown that amniotic fluid stem cells, bone marrow MSCs and other stem cells can improve ovarian function [27–31]. MSCs can protect or reactivate the spermatogonial stem cell (SSC) niche [32, 33]. Some experiments indicated that the application of MSCs led to the recovery of spermatogenesis through influencing SSC microenvironment components [34, 35]. Monsefi M et al. proved that MSCs promote tissue regeneration by releasing growth factors and cytokines that encourage remaining spermatogenic cells to proliferate and finish their division [36]. In summary, the advancement of MSCs as stem cell therapies for infertility is also an ongoing research focus in the future of infertility and requires further long-term planning.

Strengths and limitations

Compared with traditional reviews, we used widely bibliometrics tools to display the visual distribution of countries, journals, organization, authors, and keywords in the research of exosomes in infertility. However, there are still some limitations in this study. All data were obtained from the WoSCC database; therefore, articles that are not included in WoSCC cannot be collected. However, WoSCC is the most widely used database for bibliometrics analysis and includes most articles of infertility.

Conclusion

For the first time, this study conducted a multi-index bibliometric analysis of articles in the field of global infertility in the past decade. The USA and China are in a leading position in this field. The most published author is Ashok Agarwal. Cooperation between institutions is more conducive to the development of scientific research. MSCs therapy for infertility may be the hot research directions for a long time in the future. This study summarizes the main research topics in the field of infertility in the past ten years, and provides new insights for the future development and research direction of infertility.

Supplementary Information

Below is the link to the electronic supplementary material.

Data Availability

The authors will supply the relevant data in response to reasonable requests. 

Declarations

Conflict of interest

The authors declare no competing interests.