Final answer:
The embryonic stage of pregnancy usually lasts about 8 weeks, during which significant developmental changes occur in the embryo.
Step-by-step explanation:
The embryonic stage of human development lasts from the time of implantation until the end of the eighth week after fertilization. During this stage, the embryo undergoes significant changes and develops the basic structures that will become the head, chest, abdomen, spinal cord, and brain. The heart begins to beat and organs start to form and function. The embryonic stage typically lasts for about 8 weeks.