Britney Spears' 17-year-old sister has given birth to a healthy girl.

Jamie Lynn welcomed her first child via Caesarean section after an ultrasound revealed the baby might be in breech position.

She has named the latest addition to the Spears family Maddie Briann, according to American magazine People.

The Spears family, including Toxic superstar Britney, were at the hospital in McComb, Mississippi when actress Jamie Lynn gave birth this morning at 9.30am local time.

Special Delivery: Jamie Lynn Spears has given birth to a baby girl

Supportive Britney had flown in from Los Angeles yesterday, leaving life in the fast lane to be by her sister's side ahead of the birth.

The pop star arrived at the Mississippi Southwest Regional Hospital with father Jamie and brother Ryan at 9am this morning, where they joined her mother Lynne.

Jamie Lynn and Britney's father, Jamie, spoke of his delight at becoming a grandfather.

'We're thrilled, we're all absolutely thrilled,' he told America's Life & Style magazine.

Sister act: Britney at LAX on her way to be with Jamie Lynn in Mississippi ahead of the birth

Boyfriend Casey Aldridge, 19, proposed to the star in April this year - four months after she announced she was pregnant.

The younger Spears sister has been dating the 19-year-old for over two years after meeting at church.

New parents: Jamie Lynn Spears and Casey Aldridge

The pregancy caused a stir when it announced on the pages of a US magazine in December last year because of the star's tender age.

Meanwhile, big sister Britney's rounded belly has led to speculation that she may also be pregnant.

The hospital in Mississippi where Jamie Lynn Spears gave birth