Pregnant Ashlee Simpson Ross Shows Off Growing Bump: 'Excited for This Baby Boy'

Maria Pasquini

Ashlee Simpson Ross can’t wait to meet her baby on the way!

Just one week after revealing the happy news that she and husband Evan Ross are expecting a son, the pregnant singer-songwriter, 35, was all smiles as she shared a sweet tribute to her bun in the oven.

“Excited for this baby boy,” she wrote on Thursday alongside a short video in which the mom-to-be showed off her growing baby bump in a body-hugging black dress. In a fun nod to her past, Ashlee used her 2008 song “Boys” as the soundtrack for the social media post.

Hours earlier, she also made time for a workout — wearing some exercise gear from sister Jessica Simpson. “Thanks sista,” she wrote alongside the Instagram Story clip.

The little one on the way will join big sister Jagger Snow, 4½, as well as Simpson Ross' 11-year-old son Bronx Mowgli, whom she shares with ex-husband Pete Wentz.

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Ashlee Simpson Ross/Instagram Ashlee Simpson Ross

RELATED: The Cutest Photos of Evan and Ashlee Simpson Ross' Growing Family

The actress and her husband first shard their happy pregnancy news last month, breaking the news by posting a photo of themselves holding up a positive pregnancy test.

“We are pregnant and we are so excited to share it with everyone. Baby #3,” Simpson Ross captioned her post, while Ross wrote alongside his: “The fam is growing. ♥️ Ash and I can’t wait to welcome the newest addition.”

Full of sisterly love, Jessica left a sweet comment, writing, "I couldn't be happier for my favorite person on the planet!!"

"This family of 5 over here are beyond elated for YOU, Evan, BX and Jagger to expand the beautiful gift of family. Auntie of 3!!” she added. “This is hands down the most exciting news I could possibly imagine!"

When it came time to reveal the sex of their baby on the way, the singer turned to her children to help her cut into a cake, which ended up being filled with blue sprinkles.

Although the majority of the family seemed happy about the news, the couple’s daughter seemed a bit hesitant. "SO STOKED 2 MEET MY BABY BOY 🖤 as u can tell Jagger wanted a sis 😂,” Ross joked.

RELATED: Ashlee Simpson Shows Off Her Baby Bump One Week After Announcing Pregnancy with Husband Evan Ross

A source previously told PEOPLE, "Ashlee has been wanting another baby for a long time. They always wanted a big family!"

The couple tied the knot in August 2014 at the Connecticut home of the groom’s mother, singer Diana Ross.