Sikiökehityksen

Sikiökehitys, also known as fetal development, refers to the period of prenatal development from the ninth week after fertilization until birth. This stage follows the embryonic period, during which the major organ systems and body structures are formed.

During fetal development, the embryo, now called a fetus, grows rapidly in size and weight. Significant changes occur in the development and maturation of existing organs and tissues. By the end of the first trimester (around 12 weeks), the fetus has recognizable human features, and its internal organs are mostly in place, though not fully functional.

The second trimester (weeks 13-28) is characterized by rapid growth and further development. The fetus begins to move, and its movements can be felt by the mother. Hair and nails start to grow, and sensory organs, such as the eyes and ears, become more developed. The skin is transparent and covered with a fine, downy hair called lanugo.

In the third trimester (weeks 29-birth), the fetus gains substantial weight, primarily due to the accumulation of fat. The lungs mature, preparing for breathing air. The brain undergoes significant development. The fetus typically positions itself head-down in the uterus in preparation for birth. This period is crucial for the final maturation of all organ systems, ensuring the baby is ready to survive outside the womb. Sikiökehitys is a complex and precisely timed process, influenced by genetic factors and the maternal environment.