What development stage occurs from conception until the fetus is fully developed?

The correct choice is the fetus period, which refers to the stage of development that occurs after the embryonic stage and lasts until birth. During this time, the developing organism is referred to as a fetus, and significant growth and maturation happen. The fetal period is characterized by the development of bodily structures, refinement of the organ systems, and overall physical growth that prepares the fetus for life outside the womb. This stage generally encompasses roughly the second trimester (week 13) through the end of the pregnancy.

The embryonic stage occurs prior to the fetal period, lasting from conception through the eighth week of pregnancy, during which the foundational structures and major organ systems begin to form. The postnatal period refers to the phase following birth, focusing on development after the neonate is born. The neonatal stage specifically pertains to the time immediately after birth to around two weeks of age, concentrating on the transitional adjustments a newborn must make outside of the womb. Thus, the fetus period accurately captures the timeframe from conception through full fetal development just before birth.