Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
A fetus is a stage in human development that begins at the end of the eighth week after fertilization and continues until birth. During this period, significant growth and development occur, including the maturation of organs and body structures.
An embryo is an early stage of development that spans from fertilization up to the eighth week, where basic structures and organ systems begin to form.
The placenta is an organ that develops in the uterus during pregnancy, providing oxygen and nutrients to the growing fetus while removing waste products through the mother's blood supply.