It's safe to say that the prospective parents are very excited about the arrival of their little one, who is due by the end of the summer.
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Yoga teacher Hilaria shared photos of her actor husband Alec holding a tiny polka dot swimming costume.
The photo was accompanied by the caption, "Itsy bitsy teeny weeny baby bathing suits make us emotional."
Hilaria and Alec's first daughter will be the second child for the 30 Rock actor. He already has a 17-year-old daughter Ireland Baldwin with ex-wife Kim Bassinger.
Hilaria shared a photo of her baby girl's wardrobe with a pink one-piece with the phrase 'Little Sister'.
The mum-to-be posted the snaps on her Instagram account with the words, "Already looking up to her big sister @irelandbbaldwin"
Ireland, who is a model, has already spoken of her excitement at getting a baby sister.
"I'm going to be a big half sister. Woah." She tweeted when the news broke, followed by "My dad is pregnant guys."
It seems all the baby talk might have triggered some memories for Ireland who tweeted an old photo of her and her mother Kim. Ireland, wrapped in Kim's arms, is adorable in a spotty t-shirt with her hair in the same style as her mum's.
Hilaria and Alec make no secret of their love for each other, regularly sharing romantic photos with fans on social networking sites.
Alec, 55, shared a photo of him and his pregnant wife and wrote "The three of us...almost."
The pair, who tied the knot in June 2012 after a three-month engagement, revealed that they were expecting their first child together in February.
A month later, Hilaria revealed that they were expecting a baby girl.
"Alec and I are overjoyed that we are going to be welcoming a little girl into our lives," she excitedly said on TV show EXTRA.