What does the fetal period mainly signify in development?

The fetal period primarily signifies the growth and maturation of organs. This stage of development occurs from the ninth week of gestation until birth and is characterized by significant changes in size and complexity. During this time, the fetus undergoes rapid growth, and organ systems that were formed in the embryonic stage continue to develop and function more effectively.

Key developments in this period include the refinement of the respiratory and cardiovascular systems, development of the brain, and maturation of the digestive system, among others. As the fetus grows, the organs that are crucial for survival outside the womb become increasingly sophisticated and capable of functioning independently.

The other options represent stages or processes that occur at different times in prenatal development. For instance, placental attachment occurs much earlier, during the embryonic period. Initial cellular division happens at the very start of development, while the formation of basic bodily structures is primarily associated with the embryonic stage. Thus, the fetal period is distinctly focused on advanced growth and maturation, highlighting its critical role in preparing the fetus for life after birth.