Blunt, 33, who's expecting baby no. 2 with husband John Krasinski, 36, wore a printed sundress as she celebrated with her The Huntsman: Winter's War costar and friends.
Actress A.J. Johnson was in attendance at the afternoon party and posted a sweet pic with the pair on Instagram, captioning it, "An afternoon of love, laughs and friendship celebrating a special piece of my [heart] #EmilyBlunt with hostess with the mostess @charlizeafrica."
Although Blunt, who has not publicly revealed the sex of her baby, was presented with a cake that was frosted pale-blue and topped with yellow ducks, "Everything at the party was done in shades of light pink," an eyewitness tells Us Weekly. "There were pink balloons and light-pink floral centerpieces. It was very low-key."
Us Weekly broke the news exclusively in January that Blunt, who's already the mom of daughter Hazel, 2, was expecting another baby with her husband of almost six years.
The British star said in an interview in March that pregnancy is different the second time around.
"The first pregnancy is the most self-indulgent thing in the world because you get massages and prenatal yoga and hypnotherapy CDs," she told C magazine. "During this one I forget that I'm even pregnant. I'm hoisting my 2-year-old around!"
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