Fashion designer Stella McCartney gave birth to her first child on Friday morning, making her famous father, ex-Beatle Sir Paul McCartney, a grandfather for the third time.

The baby boy was born three weeks prematurely at London's private St Johns And St Elizabeth Hospital, weighing 3.3 kg (7lbs7oz). Shortly after the birth both mother and child were transferred to another hospital in Portland due to the boy’s breathing difficulties, but they are said to be fine now.

Mirror.co.uk quoted a friend of the new parents saying: "They are so very, very proud. They have been looking forward to this day for so long and now they just want to get home."

Designer’s spokeswoman added: "Stella and Alasdhair Willis are thrilled with the birth of their happy and healthy baby boy in the early hours of February 25 in London. Both mother and son are healthy and resting."

62-year-old Sir Paul together with wife Heather has reportedly visited his new grandson at the hospital. Gwyneth Paltrow and Madonna also sent congratulations to their pal Stella.

Stella McCartney, 33, married the former publisher of Wallpaper magazine, Alasdhair Willis, 34, on the Isle of Bute in western Scotland in August 2003.

The designer’s new clothing collection is to be unveiled Thursday in Paris. "Stella worked on and was able to complete the collection before giving birth," People quoted her publicist as saying. However, it is still unknown whether she will be able to attend the show.