In the new photo, Navy is shown not wearing a onesie in her namesake color, but with pink and white stripes. "Then there's this little pumpkin pie," Brittany, 30, wrote.
On Sunday morning, Brittany also shared an adorable video of Navy, showing off her big, beautiful eyes.
Aldean and Brittany welcomed Navy, their second child together, on Feb. 4. The couple are also parents to 1-year-old son Memphis, and Aldean has two daughters from his first marriage, Keeley and Kendyl.
While Navy looks cute today, Brittany admitted on her Instagram Story earlier this month that things have been a little difficult since Navy's birth.
"Navy is five weeks old today, and although that is super young, I can't believe that it's been five weeks," Brittany said in an Instagram Story post. "She's a little gassy, but she's doing awesome. I feel like I bounced back pretty quickly with Memphis, even though he was nine-and-a-half pounds. But, it's just been a little harder this time. Things are definitely different, body-wise, with baby No. 2."
She continued, "Things are a little stretchier, and not as cute as they were, pre-babies, but I have the cutest little babies in my life now, so totally worth it. But I'm saying this for you mamas out there who think you're alone. You are not alone, and even though it may look perfect on Instagram, not everyone's life is that way. I definitely have my days where I lose my s—. So you're not by yourself."
Brittany and Aldean previously said they used IVF to conceive both children.
The couple married on March 21, 2015, so they just recently marked their four-year anniversary. Aldean celebrated the occasion on Facebook, writing, "4 years and counting!! Happy Anniversary to the most beautiful person I know. So thankful I get to spend my life with you."
Aldean, 42, could make history at the Academy of Country Music Awards in Las Vegas on April 7. He will receive the ACM Artist of the Decade honor and could be the first recipient of the award to get Entertainer of the Year on the same night since Garth Brooks did it 21 years ago, notes Billboard. The other nominees for Entertainer of the Year are Keith Urban, Kenny Chesney, Luke Bryan and Chris Stapleton. Aldean has won ACM Entertainer of the Year the past three years.
This year, Aldean was also nominated for Music Event of the Year for "Drowns The Whiskey," his duet with Miranda Lambert.
The ceremony will air on CBS and is hosted by Reba McEntire.