"Our new love is here," the 37-year-old singer wrote on Twitter Sunday morning. "Luna Simone Stephens, born on Thursday, the 14th. We couldn't be happier!"

Legend's birth name is John Roger Stephens.

Teigen later posted a photo on Instagram, with baby Luna's weight of 6 lbs 11 ounces.

The couple, who have been very open about their struggle to conceive, first announced they were expecting a child in October.

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"John and I are so happy to announce that we are pregnant," Teigen wrote on Instagram. "As many of you know, we've been trying to have a baby for a while now. It hasn't been easy, but we kept trying because we can't wait to bring our first child into the world and grow our family."

Before Luna's birth, 30-year-old Teigen joked about how the baby girl would look.

"Chrissy says it's a lot of pressure because everybody says she's going to be so cute," Legend said in an interview on "Big Boy's Neighborhood" radio show on KRRL radio in February. "What if she's not that cute? Every baby is not that cute. Let's just hope that she's healthy and that's all we are focused on."

In an interview with E! News, Teigen said she hopes her daughter will enjoy jet-setting.

"I want to get her into traveling really young. As soon as someone even steps on the plane with a baby you're like, ‘Ughhh! I feel bad for them!' And that's going to be us now."

But Luna may be the first of many.

"I think I'll probably be pregnant all through my 30s," Teigen told Self magazine. "I've always pictured everyone around the table for the holidays and together once a week. It'll be heartbreaking if it doesn't end up happening, but hopefully it will. We've got some embryos on hold."

Shortly before Luna's birth, Teigen and Legend celebrated their baby with two baby showers -- one in Los Angeles and one in New York.

Many celebrities sent well wishes to Teigen and Legend on Twitter: