Hilary announced the news on Saturday with a cute Instagram video in which her husband, Matthew Koma, could be seen stroking her baby bump.
But before Hilary could share any further details of the pregnancy, she had the small matter of throwing a second birthday party for her daughter to attend to.
The celebrations began with a gorgeous cake...
Which Banks seemed to thoroughly enjoy.
There were doughnuts...
And even Trolls balloons.
And the family — minus Luca — also posed for some keepsake photos.
And once the party had wrapped up, Hilary posted an adorable and emotional message on Instagram paying tribute to her "curious, confident and brave" daughter.
"My love, my sweet sweet angel girl," Hilary's message began. "Two amazing years with your smile and your bright eyes ... It seems you yelled at me, your dad, and bro for most of this time although no one would believe that with all the happiness that pours from you when you smile!"
"Now you are curious, at ease, confident and brave," she added. "I love you so so so many times and again. Thank you for choosing us. Happy 2 boo boo."
Meanwhile, Matthew also paid tribute to both his daughter and Hilary in an emotional Instagram post where he described his wife as a "superhero," and the "glue that keeps [their] family whole".
"It's the greatest privilege of my life to be your dad and I’m endlessly proud / in awe of the little human you are, and the big human you're becoming," he wrote. "There truly are no words, pep talks, dad blogs, or what-to-expect podcasts that could’ve prepared me for the amount of joy, fullness and meaning you give me on an hourly basis."
"I'm sorry I don’t always do your hair right, make mac and cheese as good as you deserve, and subject you to car soundtracks way more appropriate for your 20's than your two's," he added.
"But thankfully you have a superhero of a mother who DOES nail the mac and cheese, rages the Trolls soundtrack with you, and dresses you A++...All while being the glue that keeps our family whole," Matthew went on.
"Between us, your big bro who smothers you with more love and cute aggression than I ever thought possible, and your future sibling who you’ll guide through 'how to get Sprinkles for breakfast,' we'll never let you down Banksy boo," he signed off.
I'm not crying, you're crying. Happy birthday Banks!
Ellie Woodward is Celebrity and Entertainment Editor for BuzzFeed UK and is based in London.