Genealogy
Most genealogists prefer to refer to a mother by her maiden name when they are constructing a pedigree, whether in chart form such as a family tree or in some written form. This convention is used because it is a concise way of presenting genealogical information. Thus they would write (or show on a pedigree chart) a child as, e.g., the son of John Smith and Mary Brown.
Genealogists often also make note of all surnames used by a person during his or her lifetime (such as those acquired from birth parents, those assigned at birth when the father is unknown or not acknowledged, those acquired at marriage, and those acquired at a remarriage). For example, an illegitimate male child abandoned at birth in Italy or in other European countries will receive no surname from either of his birth parents but, instead, will be assigned a surname -- often invented from one of the three kingdoms of nature, e.g., mineral ("Pietra"), vegetable ("Rosa") or animal ("Leoni"), or otherwise according to custom within a locality, such as "Esposito" (meaning "abandoned") or "Casa Grande" (referring to the "Domo Magna," e.g., the ospizio where abandoned) -- and, when the male child marries, he often will acquire the surname of his bride and the children born to the marriage will be baptized with and throughout their lives use as their surname the surname of their mother, passing it on to their own children.
Read more about this topic: Married And Maiden Names