The 34-year-old Australian model revealed the exciting news that she and Snapchat founder, Evan, 27, are set to become parents.
A spokeswoman for the family said: 'Miranda, Evan and Flynn are looking forward to welcoming the newest member of the family.'
Miranda is already mum to Flynn, six, who she shares with ex-husband, Hollywood heavyweight, Orlando Bloom.
Earlier this year, Miranda revealed the couple were waiting until they tied the knot to try for a baby, saying: 'I'm not planning for a child yet. Not until after we get married. My partner is very traditional. We're just waiting.'
The former Victoria Secret model is very open about staying healthy in pregnancy, and admitted to fans that she kept up with her fitness routine during her first pregnancy, focusing mainly on yoga.
She explained: 'I practiced yoga throughout my whole pregnancy and I eat really healthily and I just continued that, really. I have been working out. I've been doing resistance training and some good squats, sit-ups and all that stuff.'
Miranda and Evan met in 2014 with the former Victoria's Secret model saying that even though they hit it off together almost immediately, they began their relationship as friends.
The mum-of-one also spoke about waiting six months before introducing him to her son, Flynn.
Miranda said at the time: '[My ex and I decided] that we had to know the person for six months and feel good about them [before introducing them to Flynn].
'Evan met Flynn, so yeah, things are going well. Orlando thinks he's great. We're just a modern family now!'
The pair married in an intimate backyard ceremony at his home in LA in May, in front of just 45 family and friends with Vogue capturing snaps throughout the day.