Sikiökauden

Sikiökausi, also known as the fetal stage, refers to the period of development in viviparous organisms, particularly humans, that begins after the embryonic period and continues until birth. In human development, this stage commences around the ninth week of gestation and lasts for approximately 30 weeks. During the sikiökausi, the developing organism, now called a fetus, undergoes significant growth and maturation of its organ systems, which were largely established during the embryonic period.

Key developments during the sikiökausi include the rapid increase in size and weight of the fetus. Organs continue to differentiate and become functional. For instance, the nervous system continues to develop, leading to the formation of a more complex brain. The skeletal system ossifies, and muscles develop, allowing for movement. External features become more refined, with the development of fingers, toes, and facial features. Sensory organs mature, and the fetus begins to respond to external stimuli such as sound.

This period is crucial for the overall development and preparation for life outside the womb. The fetus gains weight, and its internal organs, such as the lungs, mature to a point where they can sustain respiration after birth. The sikiökausi is characterized by continuous growth and refinement, culminating in a fully formed infant ready for birth.