In pregnancy, from fertilization to embryo formation, and then gradually developing to meet the delivery criteria, the main stages are as follows: 1. fertilized egg formation: after the couple has intercourse, the viable sperm swims from the uterine cavity to the fallopian tube and merges with the egg to form a fertilized egg; 2. fertilized egg implantation: the fertilized egg divides mitotically to form a cell mass, transfers to the uterine cavity in about 3 days, and divides to form a blastocyst, which enters the endometrium and starts to implant in about 1 week The fetal heart and fetal buds: 6-8 weeks of pregnancy, the fetal buds and the pulsating fetal heart tube can be checked by ultrasound, the fetal gastrointestinal and liver are gradually formed, the brain, spinal cord and nerves are rapidly developing, the shape of fingers, eyes, nose and mouth are clearly visible; 4. Basic formation: 3 months of pregnancy, the fetal hands and feet can be seen moving by ultrasound, the kidneys and ureter have been formed and can be excreted; 5. Placenta formation: 4 months of pregnancy In the 4th month of pregnancy, the internal organs of the fetus are almost fully developed, the placenta is formed and starts to grow rapidly; 6. Active heartbeat: in the 5th and 6th month of pregnancy, the fetus has a very active heartbeat and its hands and feet can move freely in the amniotic fluid. The fetus hair, eyebrows, eyelashes more and more clear, can hear the mother’s voice; 7, gradually developed and mature: 7-8 months of pregnancy fetal sexual organs began to gradually develop, can distinguish the sound, the retina has formed, eyes open and close freely, lungs and gastrointestinal function is close to maturity; 8, ready to be born: 9-10 months of pregnancy fetal hearing has been fully developed, wrinkles, Cui hair relatively reduced, sexual organs have developed complete. The fetal sensory organs and nervous system developed, the bones have become hard. At this time, the fetal head has been fixed in the pelvis, has been ready to be born.