Karima El Mahroug, 19, known widely by her stage name of Ruby the Heart Stealer, gave birth to a girl called Sofia at a clinic in Genoa.
She told Sky Italia television she hoped her daughter would have "a serene and tranquil life with her family and with much love". The father is 42-year-old Luca Risso, who owns two nightclubs in the northwestern Italian city.
Berlusconi is on trial in Milan on charges he paid El Mahroug for sex in 2010 when she was 17 and legally underage and then abused his office by getting her released from police custody after she had been arrested for theft.
The so-called Rubygate scandal is part of allegations that Berlusconi held orgies in his Milan villa involving dozens of starlets and prostitutes, which badly damaged his once-buoyant popularity.
Both El Mahroug and Berlusconi deny they had sex.
The former premier, 75, faces two other trials for fraud and corruption.
He was forced from power in November after his repeated failure to pass tough austerity measures led to a collapse in market confidence in Italy and pushed its borrowing costs to untenable levels.
He was replaced by former European Commissioner Mario Monti at the head of an unelected technocrat government which is now pushing through a sweeping programme of cost cuts and tax increases.