Sikiökaudella

Sikiökaudella refers to the fetal period, which is the stage of prenatal development that follows the embryonic period. This period begins around the ninth week of gestation and extends until birth. During the fetal period, the developing organism, now called a fetus, undergoes significant growth and maturation of its organs and tissues.

Early in the fetal period, the basic structures of the body are already formed. The focus shifts to refinement and functional development. Limbs continue to grow and differentiate, with fingers and toes becoming more distinct. The head remains large relative to the body, but the facial features become more defined. By the end of the first trimester, most of the major organ systems are in place, although they are not yet fully functional.

As pregnancy progresses through the second and third trimesters, the fetus grows rapidly in size and weight. Muscles develop, allowing for movement, which can often be felt by the mother. The nervous system matures, leading to the development of senses like hearing and sight. External genitalia become distinguishable. Vernix caseosa, a waxy coating, develops to protect the skin, and lanugo, fine hair, covers the body. By the end of the fetal period, the fetus is typically ready for survival outside the womb, although premature birth still carries risks associated with underdeveloped organ systems. The fetal period is characterized by organogenesis completion and subsequent growth and functional maturation.