Implication of United States abortion policies on quantity and impact of abortion‐related research

Until June 2022, when the US Supreme Court overturned the 1973 Roe versus Wade ruling, abortions had been legal in every US state.1 However, abortion regulations differed between states, ranging from restrictive to protective, and have affected patients' access to abortion services, especially in vulnerable populations.2 Abortion regulations have further impacted physicians and medical institutes.3 Evaluative bibliometrics is the study of scientific literature and research performance. To date, little is known regarding the impact of states' regulations on scientific publications on abortions. We sought to perform a bibliometric analysis of US publications on abortions during the last five decades. This was a bibliometric analysis of US publications indexed in PubMed on the topic of abortions. We searched the PubMed platform using Medical Subject Headings fitted for abortions (Appendix S1) until December 2023. We then accessed Clarivate's Web of Science platform and retrieved all the publications identified in the search. We excluded all non-original and non-US articles (Appendix S1). We obtained bibliometric data for all articles from the iCite database, by the National Institutes of Health (NIH), based on the list of PMIDs obtained from PubMed. For the included articles, we assessed the following variables: citations per year (CPY), relative citation ratio (RCR), field citation ratio (FCR), NIH centile and funding status (Box 1). The journal impact factor was collected from Web of Science. We further calculated a combined metric score: CPY*RCR*journal impact factor. We performed descriptive statistical analysis to compare bibliometric data between ‘restrictive’ and ‘protective’ states, based on data from the Guttmacher Institute.4-7 We included publications for the years 1995–2023, as data were available for this period. States were categorised into two groups: ‘protective’ and ‘restrictive’. We excluded five states that were either categorised into both groups during the study period, or that were considered ‘middle ground’. A full description of group categorisation can be found in Appendix S1. We further evaluated bibliometrics by year and performed linear regression analysis to identify trends. As data collected were publicly available online, no institutional review board approval was requested. A total of 3920 articles were included; of those, 2524 (64.4%) originated in protective states and 1396 (35.6%) in restrictive states (Figure S1). During the study period there was a higher constant increase in the number of publications by protective states than in restrictive states (Kendall's 𝜏 = 0.766, p < 0.001 versus 𝜏 = 0.387, p = 0.003, Figure 1A), and a constant higher increase in numbers of citations per year (Kendall's 𝜏 = 0.128, p < 0.001 versus 𝜏 = 0.103, p < 0.001, Figure 1B). All citation metrics were higher among the protective states when compared with the restrictive states (Table 1, Figures S2–S4): mean CPY (2.55 ± 6.56 versus. 1.77 ± 4.00, p < 0.001), mean RCR (1.33 ± 2.94 versus 0.94 ± 1.65, p < 0.001), mean FCR (3.17 ± 1.37 versus 2.96 ± 1.72, p < 0.001), mean NIH centile (40.20 ± 29.28 versus 33.08 ± 28.48, p < 0.001), and median (interquartile range [IQR]) combined metric score (3.68 [IQR 0.57–19.63] versus 2.18 [IQR 0.22–12.87], p < 0.001). There was a higher proportion of funded studies in the protective states (931 [36.9%] versus 397 [28.4%], p < 0.001). We underline notable disparity in the quantity and scientific impact of US publications on abortions based on US states' abortion policies. Higher citation metrics in protective states reflect a significantly higher impact of articles published in these states on the scientific literature. They may also suggest that physicians and scientists could conduct research in a more supportive environment, either morally or financially. The higher funding proportions in protective states may support this hypothesis. The higher increase in the trend of absolute number of publications in protective states suggests that abortion policies have a long-term impact, but also provide evidence that policy modifications, either restrictive or protective, can still shift the pendulum. Accordingly, we can expect significant changes in the scientific literature in the near future following the recent overturn of Roe versus Wade by the Supreme Court in June 2022. Limitations of this study include the grouping of different states into two categories, excluding states that were considered ‘middle ground’, and the use of seven time points only for grouping of states, limiting the evaluation of temporal changes. In addition, we could not account for the possible impact of research on state policies, or for the effect of multistate research on the results. Scientific research has led to significant discoveries and improved health care and public health and is imperative to the well-being of patients. The observed disparities in our study may be accentuated by the recent Supreme Court ruling and subsequent new anti-abortion legislations, and measures should be taken to minimise the prospective gaps. GL and RM conceptualized and designed the work, acquired and analyzed the data, drafted the work, reviewed it and approved the final version. YB and KH acquired and analyzed the data, reviewed the work, and approved the final version. None. No funding was received for this research. RM is an Intuitive Surgical consultant. All other authors: none declared. As only publicly available data were used for the study, Institutional Review Board approval was not requested. The data that support the findings of this study are available from the corresponding author upon reasonable request. Appendix S1. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

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