Early pregnancy symptoms: Implantation period Early pregnancy is a time worth looking forward to and exciting, but it is easy to have some obvious reactions, covering physical, emotional, psychological and other factors. The earliest symptom is the embryonic implantation stage, which refers to the egg implanting in the uterine wall approximately 6-10 days after fertilization. The following symptoms may appear during this period: first, breast development, the nipple color becomes darker, and the breasts become firmer; secondly, obvious abdominal pain and persistent abdominal pain appear, which feel similar to menstrual pain but more severe.