The occasion of the birth is a very nervous time, so superstition crept into this element of the Jewish life cycle in a way not found at other times of life. If, God forbid, a child is born unhealthy and is close to death, one superstition is to rename the child so as to confuse the Angel of Death. It is surprising how many Jews will attest to the success of this method. With a similar thought in mind, we do not buy any items for the baby before the birth.
More information on birth rituals