I've never understood why people fall for horoscopes and other hocus pocus ideas that focus on when you were born, as if the arrangement of stars on the day of your birth has serious long-term implications for your life. If the stars had anything to do with our lives and what happens to us (which they don't), it should go by our conception date, not our birth date.
After all, birth is just one event in the life of a human being. One might as well look for the constellation under which a person cut their first tooth, started kindergarten, or had their first menstruation as to place emphasis on birth.
Every human individual begins life at fertilization, not birth. That's just scientific fact. Birth is something that happens to all of us, if we live long enough. But it certainly isn't when our life begins.
Of course, what stars we are born under at birth matters as little as what they look like on any other day of our lives. But while most of us see how silly it is to think the formation of stars in the sky on the day of our birth is significant, we too often place far too much significance on birth in other ways. The truth is that birth isn't magical. It doesn't bestow any new destiny or rights or personhood that wasn't already present. The same person exists before and after birth. Birth simply changes a person's location.
Because of these facts, we shouldn't view birth as the beginning of life or speak of it as if it were. Words matter. Ideas matter. It's inaccurate to view birth as anything more than an event that happens to a person. It doesn't define a person.