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The Tokophobia Severity Scale (TSS): measurement model, power and sample size considerations

Martin, Colin R.; Jones, Catriona; Huang, Chao; Jomeen, Julie; Boubert, Laura; Marshall, Claire A.


Colin R. Martin

Catriona Jones

Julie Jomeen

Laura Boubert

Claire A. Marshall


Objective: To examine the measurement model of the Tokophobia Severity Scale and consider issues of statistical power and sample size from the original instrument development study. Background: Fear of childbirth (FoC) and tokophobia represents an area of increasing concern within perinatal mental health research and clinical practice. Existing measures of the FoC have been criticised due to either measurement inconsistencies, difficulties in scoring or practical clinical application. Attempting to address these limitations, researchers developed the Tokophobia Severity Scale (TSS). A fundamental assumption underpinning the use of the TSS is unidimensionality, however this assertion may have been based on sub-optimal sample size and approach taken to factor structure determination. Method: Parallel analysis (PA), principal components analysis (PCA), exploratory factor analysis (EFA), power analysis and sample size calculation using a reconstruction of the original dataset from published summary data. Results: Following replication of the original PCA, a three-factor model was found to offer a significantly better fit to data than a unidimensional model. Power analysis suggested the original study was underpowered. Conclusion: The TSS remains a promising tool but assumptions regarding its measurement model are based on an inadequate sample size. Sample sizes for a sufficiently powered study indicated.


Martin, C. R., Jones, C., Huang, C., Jomeen, J., Boubert, L., & Marshall, C. A. (in press). The Tokophobia Severity Scale (TSS): measurement model, power and sample size considerations. Journal of reproductive and infant psychology,

Journal Article Type Article
Acceptance Date May 8, 2021
Online Publication Date Jun 9, 2021
Deposit Date May 28, 2021
Publicly Available Date Jun 10, 2022
Journal Journal of Reproductive and Infant Psychology
Print ISSN 0264-6838
Electronic ISSN 1469-672X
Publisher Routledge
Peer Reviewed Peer Reviewed
Keywords Childbirth; Emotional; Psychosocial factors; Quantitative methods; Mother/s
Public URL


Accepted manuscript (278 Kb)

Copyright Statement
©2021 The authors. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright holder

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