It takes about a week for the fertilized egg to implant and there are specific conditions: 1) disappearance of the zona pellucida; 2) differentiation of the blastocyst trophoblast from the syncytial trophoblast; 3) simultaneous development and functional coordination of the blastocyst and the endometrium; 4) secretion of sufficient amount of progesterone in the pregnant woman’s body. Soon after the fertilized egg is implanted, an increase of HCG in the blood of the subject can be measured by radioimmunoassay. Most people have no symptoms after implantation, but some may experience bleeding from implantation, back pain, dizziness, nausea, vomiting, loss of appetite, coldness, weakness and drowsiness in early pregnancy. After successful implantation, do not take random medication, avoid intense exercise, absolutely quit smoking and alcohol, strengthen nutrition, exercise appropriately and ensure sufficient sleep. Pregnant women should closely observe their condition and seek medical attention promptly in case of vaginal bleeding and abdominal pain to prevent preterm abortion and ectopic pregnancy.