Toxicity test using an organism in an early life stage such as the embryo or larva, noting that this stage is often the most sensitive part of the species life cycle.
Source:
PAC, 2016, 88, 713. 'Glossary of terms used in developmental and reproductive toxicology (IUPAC Recommendations 2016)' on page 746 (https://doi.org/10.1515/pac-2015-1202)