sikiöaikaista
Sikiöaikaista refers to a period of time during human development that occurs from the ninth week after conception until birth. This stage is characterized by significant growth and maturation of the organ systems that began to form during the embryonic period. The developing human organism is now referred to as a fetus. During this time, the fetus's body proportions become more human-like, with the head becoming relatively smaller compared to the rest of the body. Major organ systems continue to develop and become functional. For example, the nervous system continues to mature, and the skeletal system ossifies. External genitalia become more distinguishable, allowing for the determination of sex. The fetus begins to move and can swallow amniotic fluid, which aids in the development of the digestive system. Its lungs mature, and by the later stages, it may be able to survive outside the womb with medical intervention. The development during the fetal period is crucial for the infant's ability to function independently after birth.