The 25-year-old put her burgeoning bump on show as she posed in a bikini for a beach photo shoot to coincide with the announcement.
'The Lamas-Richie family is happy, healthy and definitely pregnant,' she tweeted today.
Baby news: Reality TV star Shayne Lamas has revealed she is pregnant with her first child
Bump ahead: The 25-year-old with her husband Nik Richie, whom she married last year within hours of their first introduction
Shayne, who is the daughter of US TV star Lorenzo Lamas, wed her businessman husband Nik Richie last year.
Ex: Shayne was briefly engaged to Matt Grant after winning The Bachelor in 2008
They married at the Little White Wedding Chapel in Las Vegas in April within just hours of meeting one another.
Richie, who founded the celebrity website TheDirty.com, told Radar Online: 'I'm really excited. I didn't want it to get out until I was 100 per cent ready for it but at the same time, she looks beautiful and I think she should embrace her body right now.'
He father Lorenzo, who starred in The Bold and The Beautiful and now has his own reality show Leave It to the Lamas, said: 'I'm speechless. I'm happy for them I want to be called Papa Lolo by the baby. It's easy for a kid to wrap their tongue around.'
Shayne, who played Carly Corinthos on General Hospital in 2005, won season 12 of the Bachelor and was briefly engaged to financier Matt Grant in 2008.
They called off their relationship in July of that same year.