The <scp>6Rs</scp> of <scp>EFDT</scp> Studies

Given the increased concerns over reproducibility, replicability, and reliability of scientific studies, the embryo-fetal developmental toxicity (EFDT) study was examined from this perspective together with the classic 3Rs. These 6Rs contribute to external validity (i.e., applicability to human safety). Species differences and experimental conditions lower the validity of all preclinical studies to variable extents. The apparent lack/paucity of demonstrated replicate EFDT studies lowers reliability and thus validity. I make suggestions intended to add reliability for the continued use of these studies, which are a cornerstone for assessing safety during human pregnancies. Experienced readers will recognize that the suggestions would also apply to other guideline-mandated developmental and reproductive toxicity and toxicity studies.