What is the developing baby called during first trimester?

The developing baby during the first trimester of pregnancy is commonly referred to as an embryo. This early stage begins at the moment of fertilization, also known as conception. The term "embryo" is used to describe the fetal development until the end of the eighth week of pregnancy. During this period, rapid growth and differentiation occur, transforming a single-cell zygote into a complex and well-formed human embryo with recognizable structures and organ systems.