Labour MP Laura Pidcock has announced she is pregnant and said she is "over the moon".
The 30-year-old shadow labour minister, who represents North West Durham, is due to give birth in July.
She wanted to reassure constituents that she will continue to fight for them, and has recently spoken in Parliament calling for better arrangements to be made to allow MPs who are new mothers to vote in Commons debates.
Some news! I want my constituents to know that, all things being well, I will be having a child in late July and I'm...
She has been become a high-profile MP since her election last year and is an ally of leader Jeremy Corbyn.
Her maiden speech which criticised Commons traditions and hit out at inequality was widely shared and, controversially, said she could not be friends with a Tory.
Writing on her Facebook page, Ms Pidcock said: "Some news! I want my constituents to know that, all things being well, I will be having a child in late July and I'm over the moon.
"This last year has been a bit of a whirlwind. The overriding message I want to get out is that I now consider myself to have two important roles and not one."
She linked her message to an interview with the Northern Echo in which she said: "I remain committed and passionate about politics but now I will have a child to think about and I will have to balance being a mum and an MP in what is quite an inflexible system."
Earlier this month, she backed calls from Labour former deputy leader Harriet Harman for arrangements to be put in place for when an MP has a baby or adopts a child.
Ms Pidcock said: "I am sure many women in this House who take time off to be with their baby in the first few weeks want to practise that act of democracy in representing their constituents whilst being a new mother and not denied that by the presentation that they just haven't voted."
Ms Harman agreed, and said: "Why should that constituency lose the right for the vote in their name to be cast because their MP is having a baby?"