On Friday, Pimenta and Oliveira revealed they were expecting their first child together, sharing a picture of the ultrasound and the baby bump.
"Our lives will carry out with a special company. A job that will last the rest of our journey. Anxious to meet you my love," he wrote on Instagram.
The official MotoGP page commented: "We're so happy for you and can't wait to have a new member in the paddock."
Fellow MotoGP rider Maverick Vinnales replied: "Congrats Miguel! Is the best thing you could experience in the world."
As reported by SportsBible, Pimenta is the daughter of Oliveira's father's second wife. They met in their early teens and kept their relationship secret for a long time before going public a few years ago.
"Before love there was a great friendship. We grew up together," Oliveira told Portuguese TV last year.
"At some point we realised that it was more than a friendship, it is a very strong love."
Pimenta often posts about her love for Oliveira on social media, celebrating his birthday last year with the message: "My love today is your day. There is not a day that my love for you does not grow even more."
Oliveira created history last year by becoming the first Portuguese rider to win in the elite division of the sport.
"I saw this coming already quite a few races ago," he said. "I felt we had the potential to do it, so finally to be able to do it is a huge boost to be able to continue like this."
Oliveira is eighth on the MotoGP riders' standings with 85 points and three podiums. The season will resume on Sunday, August 29 with the British Grand Prix at Silverstone.
