Definition: Illegitimate birth

Category: Social statistics

The birth of a child to a mother who, according to national law or customs, was not married at the time of the birth. 

This term should not be used to explicitly
describe the child on the birth certificate unless specifically required by national law, but rather may be considered as a statistical term for counting such births to describe the number of out-of-wedlock births which have occurred. http://ec.europa.eu/eurostat/ramon/statmanuals/files/SeriesF_84_EN.pdf