Retained fetal membranes in C57BL/6NCrl mice: description of clinical case presentations and related epidemiologic findings

Comp Med. 2011 Dec;61(6):505-9.


During a triinstitutional study to test whether individually ventilated caging systems impaired welfare and reproduction relative to static housing systems, varying numbers (2 to 7) of discoid-shaped, fleshy structures were found in utero of 17 postpartum female mice on study. Further investigation revealed these structures to be retained fetal membranes (RFM). A point prevalence of 24.3% was calculated based on a total population of 70 postpartum female mice on study. This finding was preceded by 3 typical clinical presentations, which are described here. We designed a case-control matched cross-sectional epidemiologic study to identify associated risk factors and antemortem indicators of RFM. Housing on the bottom shelves and attachment to the rack systems were factors associated with a diagnosis of the condition. In addition, neutrophilia, monocytosis, lymphopenia, and decreasing hematocrit values were associated with the diagnosis of RFM. These results confirmed that a CBC can be a useful antemortem screening test for the identification of affected mice. We conclude that RFM are likely an incidental finding although they may present concurrent with other pregnancy complications.

Publication types

  • Multicenter Study

MeSH terms

  • Animals
  • Blood Cell Count
  • Case-Control Studies
  • Cross-Sectional Studies
  • Extraembryonic Membranes / pathology*
  • Female
  • Hematocrit
  • Housing, Animal*
  • Likelihood Functions
  • Logistic Models
  • Mice
  • Mice, Inbred C57BL
  • Myeloid Cells
  • Postpartum Period
  • Pregnancy
  • Pregnancy Complications / epidemiology
  • Pregnancy Complications / pathology
  • Pregnancy Complications / veterinary*
  • Prevalence
  • Risk Factors
  • Rodent Diseases / epidemiology*
  • Rodent Diseases / pathology*