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Review
. 2026 Feb 27:109206.
doi: 10.1016/j.reprotox.2026.109206. Online ahead of print.

IDENTIFYING AND REPORTING DYSTOCIA IN LABORATORY RODENTS

Paul Barrow  1 , Prägati S Coder  2 , Rashin Ghaffari  3 , Leah Zorrilla  4 , Christopher J Bowman  5 , Curtis E Grace  6 , Jason Manton  7 , Alan Hoberman  8 , Narinder Barraclough  9 , Isabelle Leconte  10 , Nicola Powles-Glover  11 , Shermaine Mitchell-Ryan  12
Affiliations
Free article
Review

IDENTIFYING AND REPORTING DYSTOCIA IN LABORATORY RODENTS

Paul Barrow et al. Reprod Toxicol. .
Free article

Abstract

Dystocia (prolonged, difficult, and/or delayed parturition) results from a variety of potential clinical conditions including uterine inertia, hormonal imbalances, oversized fetuses, abnormal orientation of fetuses in the birth canal, etc. In the laboratory, dystocia frequently results in euthanasia. In 2020, the Health and Environmental Sciences Institute's Developmental and Reproductive Toxicology committee formed a working group to discuss anecdotal reports of increased incidence of dystocia amongst laboratory rodents. Based on an initial survey completed by contributing laboratories, it became apparent that there is significant disparity in how various laboratories define, record, report, and interpret dystocia in laboratory animals. This report highlights the key findings from a survey of performing laboratories conducted by this working group and proposes best practices and recommendations for the monitoring and recording of parturition and dystocia in reproductive toxicity studies in rodents. Implementing consistent definitions, observation strategies, and documentation standards will strengthen data comparability and enhance the scientific foundation on which regulatory decisions are made. Furthermore, consistent reporting of dystocia across industry laboratories will improve the transparency and reliability of evidence used in hazard identification and risk assessment and thereby help reduce discrepancies in regulatory outcomes and facilitate regulatory decision-making for chemicals, plant protection products, biocides, and pharmaceuticals.

Keywords: Dystocia; Gestation; Parturition; Rat; Rodent.

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Conflict of interest statement

Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper Declaration of competing interests The authors declare the following interests: Paul Barrow is an independent consultant based in Basel, Switzerland. Prägati S. Coder is an employee of Charles River Laboratories, Ashland LLC. Rashin Ghaffari is an employee of Corteva Agriscience. Leah Zorrilla is an employee of Bayer Crop Science. Christopher J. Bowman is an employee of Pfizer, Inc. Curtis E. Grace is an employee of Merck & Co., Inc. Jason Manton is an employee of Toxiqua Ltd. Narinder Barraclough is an employee of Labcorp Harrogate, UK. Nicola Powles-Glover is an employee of ExxonMobil. Shermaine Mitchell-Ryan is an employee of the Health and Environmental Sciences Institute (HESI), a non-profit organization that facilitates collaborative scientific research among academia, government, and industry. Alan Hoberman and Isabelle Leconte were employed at Charles River Laboratories during the initial drafting of this manuscript and are now retired. The work described herein was conducted as part of a collaborative scientific effort under the HESI Developmental and Reproductive Toxicology (DART) Committee. The authors declare no other known competing financial interests or personal relationships that could have appeared to influence the content or conclusions of this work.

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