The Atomic Kitten singer, 31, and 34-year-old 5ive star Ritchie have been together since they both appeared on ITV2’s The Big Reunion last year.
Natasha, who is already mum to three boys, revealed her excitement to OK! magazine, saying: “We did it… we made a girl!
“Little girls have been so on my radar, I see them with pigtails and frilly socks with their mums and I still can’t believe I’m having a mini-me!”
Despite only being together since last year, Natasha admitted she is hoping Ritchie will pop the question soon.
She said: “I’m just waiting for the wedding ring now, to be honest.”
But Ritchie told the magazine, “We’ll see. Natasha said she wants our little girl walking if we do [get married]”
Meanwhile, Natasha’s baby bump stole the show on the red carpet at the BAFTAs this week. The five-months pregnant star wowed in a figure-hugging blue maxi dress and was definitely glowing.
Speaking of her pregnancy, she said: “I’ve been very hormonal and very sick. I’ve been very tired. I thought number four, it’ll be a breeze but it’s been tough. It’s been hard work, the hardest one yet.”