Discrepancies in Embryonic Staging: Towards a Gold Standard

Area of Science:

• Developmental Biology
• Embryology
• Human Development

Background:

• The Carnegie staging system has been the standard for human embryo development chronology for over 50 years.
• Despite its universal application, significant variations exist in published Carnegie staging reference charts.
• This variability complicates a clear, unified understanding for embryologists and medical professionals.

Purpose of the Study:

• To investigate the existence and characteristics of a gold standard for Carnegie staging.
• To provide a clear overview and analysis of variations in published Carnegie staging charts.
• To identify potential factors contributing to these discrepancies.

Main Methods:

• A comprehensive literature review was conducted, identifying 113 publications.
• Screening and full-text assessment reduced the pool to 26 relevant publications.
• Nine publications underwent critical appraisal to analyze data variations.

Main Results:

• Consistent variations were observed in datasets, particularly in embryonic age (up to 11 days difference) and embryonic length.
• Potential causes for variation include differences in sampling, evolving technology, and data collection methods.
• Prof. Hill's Carnegie staging system emerged as a potential gold standard from the reviewed literature.

Conclusions:

• Significant variations in Carnegie staging charts hinder a unified understanding of human embryo development.
• Prof. Hill's Carnegie staging system is proposed as a potential gold standard due to its consistency within the reviewed data.
• Further standardization efforts are needed to address discrepancies in embryonic age and length measurements.