Final answer:
The three periods of prenatal development are the germinal, embryonic, and fetal stages. In the germinal stage, the fertilized egg undergoes rapid cell division and implants into the uterine lining. The embryonic stage is characterized by the formation of body and organ structures, and the fetal stage is a period of rapid growth.
Step-by-step explanation:
Three Periods of Prenatal Development and Major Milestones;
The three periods of prenatal development are the germinal, embryonic, and fetal stages. In the germinal stage, which lasts approximately 2 weeks, the fertilized egg (zygote) undergoes rapid cell division and implants into the uterine lining. The embryonic stage, lasting about 6 weeks, is characterized by the formation of body and organ structures, including the development of the neural tube. Finally, the fetal stage begins at 9 weeks and continues until birth, during which time the body, brain, and organs grow rapidly.