Being overheard by your child while talking about them is a powerful parental tool at any stage of your child's development and growth. Children eavesdrop, initially and at times of stress, as a survival instinct; in fact, they do it for fun throughout their lives – even as adults! It is best to avoid discussing a problem you think your child has on the phone or in earshot of your child regardless of whether it appears they are listening or not. They most likely are!
Better yet, find ways to positively utilize their eavesdropping behaviors. Let your child overhear you talking about them as if the child is precisely the way you want them to be, whether they match with your expressed image or not. Within a week or so, you may notice they begin acting consistently with the way they overheard you describing them. Parent Power is the concept that children believe what they hear their parents say about them. They live up to or down to what they overhear from their parents, modeling their actions after their parents' idea of who they are.