The singer has named her first child with husband Josh Duhamel, Axl Jack Duhamel, thought to be inspired by Guns N' Roses frontman Axl Rose.
A representative for the singer said Axl weighed 7lb 10oz (3.5kg).
In February, 'Transformers' star Josh spoke to The Huffington Post UK about Fergie's pregnancy, saying "how cool it is to know that every time I look at her, this little thing is growing. It's amazing just going through that".
The 38-year-old singer married the 40-year-old actor in 2009. She officially changed her name from Stacy Ann Ferguson to Fergie Duhamel this month.