Angelina Jolie laughed with joy as her newborn twins were delivered and partner Brad Pitt cut their umbilical cords, according to reports.

The couple, who welcomed son Knox Leon and daughter Vivienne Marcheline on Saturday, were together and "calm" during the delivery, with their doctor joking how Pitt "was my assistant."

The actress delivered her twins by Caesarian section at the Fondation Lenval hospital in Nice, France, and there were "absolutely no problems" with the birth.

Jolie's obstetrician, Dr Michael Sussman, tells People.com, "It was an epidural, so (Angelina) was awake and speaking and laughing. They were happy."

"He (Pitt) was ... perfectly calm, totally determined, very pleased to be at the birth of his children, very moved and very emotional."

And when asked how long Jolie was expected to stay in hospital for, he said, "I don't know. She will stay for a few days. You know, in Europe it isn't like in the United States, where the patients go home after three days. They will stay a bit longer until everything is okay."

"The babies are fine. The babies are with the mother and father and they are fine."