On Saturday, Arnold posted a mirror selfie, showing off her tummy in a bralette and sweatpants.
"11 days postpartum 💕 feeling incredibly grateful for this body that carried our sweet Sage and is now feeding her and taking care of her," she wrote. "I think it's easy to only feel grateful for our bodies when we feel we are at our tip top shape but I have truly never felt more proud of my body and it's tired/sore muscles, sore nipples 😂, and my new c section scar that will always remind me of the most special day of my life when we got to hold our little girl for the first time."
The new mom added that she is going to "try and remember this feeling forever and focus more on loving my body because of what it does for me rather than how I look."
On Nov. 2, Arnold announced that she had given birth, alongside the first photo of herself with Samuel and their newborn.
In May, Arnold told ET about the exact moment she found out she was pregnant while on tour with her fellow DWTS pros.
"I found out I was pregnant on tour in a hotel room by myself. I had a day off, and I think I was in Kansas City. I just remember waking up that morning and being like, 'I think I am pregnant, I think I am.' So I went to CVS by myself, I got a test and took it," she shared. "Sam and I saw each other about a week after. I kind of debated if I would tell him over the phone, and I was like, 'No, I absolutely have to tell him in person.' So I kept the secret to myself for about a week and it was very hard, if you know me."
Just days before she gave birth, ET chatted with Arnold and fellow DWTS pro Witney Carson, who is also pregnant with her first child.
"I just can't believe it. Witney and I are sitting here both pregnant, chatting with Entertainment Tonight!" Arnold gushed. "It's actually insane. We've done so many things in our lives together, so it's like, naturally, why wouldn't we get pregnant together? It's so funny because you can't really plan a pregnancy. I mean, you can plan when you want to try, but it's not like it's always going to happen when you want it to."