Implantation is the major sign of pregnancy for various women, it is a stage in which a zygote of fertilized egg limplants into the wall of the uterus.
Implantation usually takes place 6 to 10 days post ovulation, or day 20 to 24 of a menstrual cycle. However, it can take place a few days later or earlier. Once fertilization takes place, the egg remains the fallopian tuve for three days prior of getting inside the uterus and starts to implant itself to the walls of the uterus.