Natalie Portman welcomes a son with fiancé Benjamin Millepied

Natalie Portman and her fiancé Benjamin Millepied  are celebrating the arrival of a baby boy. People magazine broke the news of the birth, but no other details have been released.

The couple, who met on the set of the film Black Swan, have made no secret of their delight at the thought of becoming parents.

Although usually protective about her private life, Portman, 30, started to speak more openly since announcing her pregnancy.

When she accepted her Best Actress Oscar earlier this year, she paid tribute to her French husband-to-be, saying: 'My beautiful love, Benjamin, who has now given me my most important role of my life.'

Speaking about motherhood, she admitted: 'I'm sure I'll make lots of mistakes, but I'm open to learning.'

Portman also revealed that she has relaxed her strict vegan diet in order to nourish her growing child properly.

'I actually went back to being vegetarian when I became pregnant, just because I felt like I wanted that stuff,' she said.

'I was listening to my body to have eggs and dairy and that sort of stuff.

'I know that there are people who do stay vegan. But I think you have to just be careful, watch your iron levels and your B12 levels and supplement those if there are things you might be low in in your diet