Mila Kunis, Ashton Kutcher expecting first baby together

Mila Kunis and Ashton Kutcher are expecting their first child together, reports say. Photo/AP

Mila Kunis is pregnant.

The 30-year-old actress is expecting her first child with That '70s Show co-star Ashton Kutcher, to whom she recently got engaged.

A source told People.com: "They are both very, very happy. It's still early."

The couple sparked engagement speculation after Kunis was spotted with a huge diamond ring last month, but the loved-up stars aren't expected to rush down the aisle in light of their baby news.

The insider added: "It won't necessarily be a short engagement. They haven't begun planning the wedding yet."

Meanwhile, E! News reported that Kunis was recently seen at a prenatal class in Los Angeles.

The couple began dating in 2012 following Ashton's split from ex-wife Demi Moore, but they have known each other for years after playing the lead roles in hit 1990s sitcom That '70s Show.

Kutcher, 36, is thought to have had a crush on his gorgeous co-star when they worked together, but their romance didn't blossom until years later.

A source previously said: "He was so in love with [Mila] for a while when they worked together. He thought she was a goddess, was always talking about how beautiful she is."

Jupiter Ascending star Kunis recently opened up about her low-key date nights with Ashton, revealing they enjoy "white T-shirt nights".

She explained: "We have a thing called white T-shirt night and it's when you wear jeans and a white T-shirt and you go on a date. Nothing fancy, it's just something that you love to do - whether that's bowling or dinner or going to a cheese shop and have some wine or walking around. I think that's just the best thing to do, and sometimes it's just nice to stay home."

- Bang! Showbiz