A Melbourne woman who repeatedly had sex with a 13-year-old boy-next-door and had three of his children has escaped jail.

The woman, who cannot be named, started having sex with her teenage neighbour in August 2004, when she was 22.

Victorian County Court Judge Christopher O'Neill sentenced her to three years in prison, wholly suspended for three years.

The woman now has six children and Judge O'Neill said her family circumstances had to be taken into account in the sentence.

"Normally offending of this seriousness would warrant a significant jail sentence," Judge O'Neill said on Friday.