Key time slot of foetus' development

Pregnant for the 4th weekend: The embryonic forms of nervous system and circulation organ have nearly all already taken shape, the heart has beaten since about the third week. Pregnant for the 8th weekend: The foetus' most viscera organs have already developed, the brain begins to develop fast. Pregnant for the 20th weekend: Can hear the foetus' heartbeat with the doctor's stethoscope, you can feel the fetal movement. Pregnant for the 36th weekend: Organs such as the foetus' circulation, breath, digesting,etc. have already reached maturity, has planned to be born to mother's lower abdomen.