Erin Napier Shows 4-Week-Old Baby Girl Mae's Growth While Bottle-Feeding Formula: 'Plumping Up'

Erin Napier's baby girl is growing so fast!

The HGTV star, who welcomed her second baby daughter Mae on May 28, documented the 4-week-old's growth after previously revealing that she was bottle-feeding her formula. On Instagram Sunday, Erin shared a photo of the infant's legs and arms while writing that she is "plumping up."

Earlier this month, Erin, who shares Mae and 3-year-old daughter Helen with husband Ben Napier, opened up about feeding her new addition with formula, just like she did with her firstborn.

"Just a little encouragement for you mamas who weren't able to breastfeed, like me. Don't let anyone make you feel less than or belittled because of it," she wrote alongside a photo of herself bottle-feeding the newborn.

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"Helen was a formula baby and has no allergies, has always been a healthy weight, and is just as in love with and attached to her mama as her breastfed friends are to theirs," Erin continued. "Formula is our friend at this house! Just watch as these little matchstick legs get chunky and strong."

Ben and Erin announced their pregnancy news in April, telling PEOPLE at the time that they found out in September while simultaneously filming Home Town in Laurel, Mississippi, and their new show, Home Town Takeover, about 200 miles away in Wetumpka, Alabama.

The HGTV couple wasn't sure if they'd be able to start a family due to a complicated, years-long health battle Erin had faced, they previously shared with PEOPLE.

erin napier/ instagram

For a decade, starting when she was 19, the designer suffered from bouts of severe stomach pain that would leave her bedridden for days. She saw countless specialists before an emergency exploratory surgery in 2014 finally revealed the cause: she had a perforated appendix.

Her appendix had been bursting and healing repeatedly for years causing her organs to become wrapped in scar tissue and bound together. But even after doctors removed the tissue, she was told the damage done would make it unlikely she would be able to have children.

"I was very sad. And not knowing is always the biggest hurdle for me to overcome. I like to have proof. And we had no proof that I would be able to have kids," she told PEOPLE in 2018.

Celebrating the birth of her second baby, the parents told PEOPLE, "While we are excited to have another daughter to love, we are more excited to see the bond she and Helen will have. They're already so in love with each other!"