The Victoria's Secret model announced in March that she was expecting her second child with husband Marko Jaric.
© Rex Features
© WENN
She has now announced on Twitter that she has given birth to her daughter, a sister for 2-year-old Valentina.
"Marko and I are overjoyed to welcome Sienna into our family and Valentina is looking forward to becoming a big sister!" she wrote.
Lima has previously said that she would like a "big family" with Jaric.
She has also revealed that she felt "beautiful", "sexier" and "more womanly" after giving birth to Valentina in 2009.
