The 34 year old singer shared a picture of her baby girls' tiny feet on her Twitter page, admitting she can't get over how 'tiny and perfect' they are.
Jenny welcomed the girls into the world on the 20th, before sharing the news via Twitter on Thursday morning.
She wrote: 'Good morning,Our girls are here.....Blake & Nico arrived on Sunday night.They are perfect....tiny but perfect!!'
The former pop star's due date wasn't until February, but both mum and babies are doing well following their premature arrival. Nico and Blake are her first children with husband Vincente Juan Spiteri.
Jenny had shared her pregnancy with her fans, posting snapshots of her expanding bump online. She also revealed that despite getting bigger in size, Vincente, 38, loved her voluptuous pregnancy figure.
Before giving birth to the twins she told Closer magazine: 'It's Vinnie's first time as a dad and he can't wait, but he's more excited right now about my new lumps and bumps. Let's just say he's very happy with my extra pounds!'
For more information on pregnancy health and advice go to www.nhs.uk/Start4Life