Pregnancy is usually not detected six days after intercourse. The fertilized egg is formed after the sperm meets the egg and is transported to the uterine cavity through the peristaltic movement of the fallopian tubes, where it takes about 6-7 days to implant. After the fertilized egg is laid in the uterine cavity, an embryo is formed, which grows and develops, and the trophoblast cells of the placenta begin to secrete large amounts of hCG to supply the embryo with the necessary nutrients for growth. Therefore, couples who are preparing for pregnancy should not be too anxious, and maintaining a good physical condition and state of mind will help them to conceive successfully. In addition, it is recommended that couples take oral folic acid 3 months before pregnancy preparation to avoid the possibility of fetal malformation.