kimora Lee Simmons with her husband Time Leissner Araya Diaz/Getty Images

Kimora Lee Simmons, 39, is reportedly expecting her fourth child.

According to the New York Post, the model-turned-fashion designer is four months pregnant with her first child fathered by husband Tim Leissner, who is an investment banker.

The happy couple were recently spotted celebrating the news over dinner at Gallaghers Steakhouse in New York and are said to be over the moon.

Simmons has two daughters - Ming, 14, and Aoki, 12 - with ex-husband Russell Simmons, 56, and a son - Kenzo, 5 - with actor Djimon Hounsou.

Leissner is no stranger to family life as he already assumes a step-dad role to Kimora's children and has frequently been spotted on family vacations with the clan over the past year.

Leissner in St Barts with Kimora Lee Simmons and her children, 2014 Getty

Simmons and Leissner are said to have tied the knot in top secret ceremony in 2013 but news of the nupitals only became public after her ex-husband spoke out on Twitter.

Dismissing claims that his former wife was dating rapper Birdman, Russell Simmons tweeted: "All of us love @OfficialKimora but the fact is she is happily married.. Tim is has been family for a for a while now. #gossipcop..."