After fertilization, the egg moves towards the uterus and after about 6–10 days attaches to its wall. This natural process causes slight damage to the endometrium and may be accompanied by minor bleeding.
These false periods occur already during pregnancy, but often the woman does not yet know that a new life has arisen inside her. This is where the common myths arise that “it turns out I was already pregnant, but I was still getting my period.” Implantation bleeding is characterized by a small amount of discharge and lasts 1-2 days, so it can be confused with regular menstruation, which for some reason came a little earlier than expected and passes surprisingly easily.
There's no need to worry. Rather, this is a reason for joy: with a high probability, these unexpected “periods” during pregnancy are a sign that you will become a mother.