Author responseAuthors: Amy Elsmore1,2, Gbenga Alayande3, Elizabeth Mainwaring4, Mahfam Jafarpour2, Michael P Rimmer5,6, Neil Cockburn7, Jason Curtis8, Ragave Ilaalagan1, Bassel Al-Wattar9,10, Sarah Bell11, Bala Karunakaran1, William Parry-Smith*1,2, Pensee Wu *2,12,13.*joint senior authorsCorrespondence: Amy Elsmore, Department of Obstetrics and Gynaecology, The Shrewsbury and Telford NHS Trust, Telford, UK. Email: a.c.elsmore@keele.ac.ukAuthor Affiliations:Department of Obstetrics and Gynaecology, The Shrewsbury and Telford NHS Trust, Telford, UKSchool of Medicine, Keele University, Keele, Staffordshire, UKDepartment of Obstetrics and Gynaecology, The Royal Wolverhampton NHS Trust, Wolverhampton, UKSchool of Medicine, The University of Cambridge, Cambridge, UKThe Centre for Reproductive Health, Institute of Regeneration and Repair, University of Edinburgh, UKEdinburgh Fertility Centre, Simpsons Centre for Reproductive Health, NHS Lothian, United KingdomDepartment of Applied Health Science, University of Birmingham, Birmingham, UKShrewsbury and Telford Health Libraries, The Shrewsbury and Telford NHS Trust, Telford, UKClinical Trials Unit, Faculty of Health Medicine and Social Care, Anglia Ruskin University, Chelmsford, UKBeginnings Assisted Conception Unit, Epsom and St Helier University Hospitals, London, UKDepartment of Anaesthesia, Cardiff and Vale University Health Board, Cardiff, UKDepartment of Obstetrics and Gynaecology, College of Medicine, National Cheng Kung University, Tainan, TaiwanAcademic Department of Obstetrics and Gynaecology, University Hospital North Midlands, Stoke-on-Trent, UKDear Dr. Aris Papageorghiou,We thank Dr Dong and colleagues for their thoughtful letter (1) in response to our systematic review and meta-analysis examining the influence of race, ethnicity, and socioeconomic deprivation on postpartum haemorrhage (PPH) in high-income countries (2). We are pleased that our work has stimulated discussion in this important area, and we welcome the opportunity to respond to the methodological considerations raised.First, regarding risk of bias assessment, we acknowledge that no single tool is without limitations. We selected the Newcastle-Ottawa Scale (NOS) as it remains one of the most widely applied instruments for observational studies and is recommended by the Cochrane Non-Randomised Studies Methods Group (3). While the GRADE approach provides a valuable framework for rating certainty of evidence (4), its application to disparity-focused observational data remains complex. We therefore considered the NOS the most pragmatic and transparent choice for this review.We agree that pooling retrospective and prospective study designs introduces potential variability. Our review incorporated both in order to provide the most comprehensive evidence base, and we undertook sensitivity and subgroup analyses to mitigate this. We also explicitly acknowledged variation in PPH measurement and ethnicity classification across studies as an important limitation.With respect to publication bias, we used funnel plots in line with PRISMA guidance (5). While statistical tests such as Egger’s regression may provide additional insights, their interpretation is challenging in the presence of substantial heterogeneity and a large number of studies. We therefore opted for visual assessment supported by transparent discussion of potential bias.In addition, we recognise the challenge posed by high heterogeneity. We addressed this through leave-one-out analyses, and subgrouping by region, time period, and adjustment for confounders. We agree that meta-regression could further explore sources of heterogeneity, though this was beyond the scope of our review and is an important area for future work.Finally, we share the concern regarding harmonisation of socioeconomic and ethnicity measures. Our review highlighted this as a key limitation, and we specifically recommended the adoption of standardised classification systems and core outcome sets to strengthen future research.In summary, while we acknowledge the methodological complexities inherent in synthesising international data on disparities in PPH, we believe our review represents an important step in consolidating the available evidence. We hope our findings encourage improved data collection and methodological refinement, ultimately supporting interventions to reduce inequalities in maternal health outcomes.Sincerely, Amy Elsmore, on behalf of the authorsWord count 402ReferencesDong et al. Letter to the editor: Methodological concerns in the analysis of racial and socioeconomic disparities in postpartum haemorrhage. BJOG manuscript ID BJOG-25-1482Elsmore A, Alayande G, Mainwaring E, et al. Effects of race, ethnicity and socioeconomic deprivation on postpartum haemorrhage in high-income countries: a systematic review and meta-analysis. BJOG . 2025. doi:10.1111/1471-0528.18278Reeves BC, Deeks JJ, Higgins JPT, Wells GA. Including non-randomized studies. In: Higgins JPT, Green S, eds. Cochrane Handbook for Systematic Reviews of Interventions . Cochrane, 2017.Guyatt GH, Oxman AD, Vist GE, et al; GRADE Working Group. GRADE: an emerging consensus on rating quality of evidence and strength of recommendations. BMJ . 2008;336:924–926.Page MJ, McKenzie JE, Bossuyt PM, et al. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. BMJ . 2021;372:n71.

Abstract Background Postpartum haemorrhage (PPH) is a leading cause of mortality and morbidity globally. While studies have revealed disparities in maternal and fetal outcomes, disparities in PPH risk within diverse populations remains understudied. Objectives To quantify the association between maternal race, ethnicity, deprivation and the risk of PPH in High Income Countries (HIC’s). Search strategy A systematic search of MEDLINE, CINAHL, EMBASE and Google Scholar from inception to 20 th August 2024. Selection criteria Observational and experimental studies from HICs that reported the outcome of PPH, in at least two racial, ethnic or socioeconomic groups. Data collection and analysis Two reviewers performed independent data extraction. Random-effects model was used to estimate risk. Subgroup analysis was performed by geographical region and time period. Main results 79 studies with 169,579,388 women were included. Women from an ethnic minority background had an increased risk of PPH, compared to White women. This effect was seen across Black women (OR 1.16, 95% CI 1.09,1.23), Asian women (OR 1.33, 95% CI 1.27, 1.39), Hispanic women (OR 1.20, 95%CI 1.12, 1.29), and women from the minority ethnic group within a given study (OR 1.13 95% CI 1.03,1.24). Eight studies reporting PPH per socioeconomic group reported increased risk of PPH for those living in socioeconomic deprivation. Conclusions Women from an ethnic minority background or exposed to socioeconomic deprivation had an increased risk of PPH in high income settings. Standardisation of data collection on ethnicity, race and socioeconomic status is crucial for future research to accurately quantify and address these disparities. Funding: There was no funding source for this study. Keywords: Maternal health disparities, ethnicity, race, socioeconomic deprivation, postpartum haemorrhage