Chrissy Teigen on Watching Her Kids "Love" on Baby Esti and Finding Her "Confidence" as a Mom

Chrissy Teigen has done this all before — the nappy changes, the late-night feedings, the bleary-eyed happiness. Except this time around, with baby number three, there's a new element at play: confidence.

"Always expect that everything's going to change and evolve," Teigen, 37, says with the wisdom of a seasoned parent. She and husband John Legend welcomed youngest daughter Esti Maxine on Jan. 13, adding to their brood, which already included son Miles, 4, and daughter Luna, 6. This assuredness is new-ish, though, Teigen admits. "I went into it very nervous with Luna. Of course, first baby, you're like, 'Oh my God, what do I have to expect? Can I hold her like this? My milk tastes gross to her. I had garlic. Is that going to give her gas?'" she recounts to POPSUGAR while speaking about her partnership with the Cord Blood Registry. "It's just like, there's so much to worry about the first time around. The second time around, you're much more relaxed, but you're still on edge because you have this other little one that needs so much attention, too."

But "then three is just like, 'Oh my God, we're so outnumbered, and they're going to survive somehow, and we're just going to go in. We're going to dive head first and it's going to be crazy, but everything's going to work out.'"

Luckily, she has a fantastic partner in Legend ("We're usually very much on the same page," the "Cravings" cookbook author says) — and, this time around, her older children. "They really do love it," Teigen says of Miles and Luna's approach to big brother- and sisterhood. "They really adore her. They beg me to pick them up from school with her. They fight over who gets to push the stroller. Miles is always kissing on her so hard. Luna holds her like a pro. . . . She has such a confidence about her, and it's so effortless for her to be a big sister. It's so cool."

Esti actually has a hoard of older girls looking out for her. Teigen serves as Luna's Girl Scout troop leader, so there will be an entire crew at her Los Angeles home, fawning over Esti. "It's really incredible," she says. "They're so natural with it. And they'll be gathered around watching her take a bath, and they just think it's so cute. But what I love is I expected that from Luna and her girlfriends, but Miles is just such a little love bug with her, too. He just adores her. I mean, his attention span is so quick, but he'll give it his all for that time that he wants to give. And it's really cute to see."

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All these moments are just a part of Teigen's "evolution" as a parent into, admittedly, "being a bit cocky about it." She elaborates, "Like knowing that you're doing things right. And even if you're doing things wrong, it's going to be OK and you'll figure it out."

One thing she did figure out years ago was making the choice to opt for cord-blood banking, she tells POPSUGAR as part of that aforementioned partnership with Cord Blood Registry, the largest private newborn-stem-cell bank in the world. Cord-blood and cord-tissue samples are taken at birth and stored for potential future medical use should the child need them. Teigen opted to bank cord blood for all three of her children. "Science is always changing, and just having been through IVF and knowing that there's so many advancements in IVF every single year," she says. "That whole world has always been so fascinating to me, and I've always wanted to be a part of it. . . . It's really important for me to let other people know that this is an option and it's something that they can do to keep their families safe and healthy for years to come."

There's a lot of noise to navigate in the health space, Teigen says, noting that recommendations can be especially overwhelming in the Los Angeles community. "I like things that are backed by science personally," she says. "So this was the easiest choice on the planet."