sikiökehitystä

Sikiökehitys, or fetal development, refers to the stage of prenatal development following the embryonic period and preceding birth. In humans, this period typically begins around the ninth week of gestation and continues until delivery. During this phase, the developing organism, now called a fetus, undergoes significant growth and maturation of its organs and systems, which were largely formed during the embryonic stage.

The fetal period is characterized by rapid increase in size and weight. Major organ systems continue to develop and become functional. For example, the nervous system becomes more complex, and the limbs continue to grow and refine their movements. Bones begin to ossify, and muscles develop. External features become more distinctly human, with the development of fingernails, hair, and facial features.

Towards the end of the fetal period, the fetus gains significant body fat, which is crucial for thermoregulation after birth. Organ systems, such as the lungs and digestive system, mature further, preparing the fetus for independent life. The fetus also develops reflexes like sucking and swallowing. This period is critical for the overall development and viability of the newborn.