Chrissy Teigen Keeping Second Child's Gender a Secret

Chrissy Teigen is always ready to open up on social media about her daily life, but there are certain things she wants to keep private. That includes her new baby's gender.

"We're not ready to say what it is yet," Teigen told PEOPLE on Thursday while promoting Lip Sync Battle LIVE: A Michael Jackson Celebration.

Teigen also told the site that she and husband John Legend conceived through in-vitro fertilization again.

"We did the harvesting — as they call it — again, where they make the embryos," the supermodel said, adding that they knew she was expecting 11 days after the treatment.

"You get the phone call and you're like, 'Please, please, please,' and then you get the result and then you're so excited," she told PEOPLE. "It does make for a very long-feeling pregnancy because you know so early."

"I think I randomly tweeted that you know those people where you're like, 'Oh, it feels like you've been pregnant forever,' and you're like, 'Hey, screw you!' I'm going to be that person," Teigen continued. "It feels long."

Although she will not talk about the baby's gender, Teigen did talk about the baby-naming process. She said it is "tough" to find the perfect name. They did not even hit on Luna for their first child until three days after she was born.

Teigen told PEOPLE one idea they have is looking at Legend's music career for inspiration.

"It's hard," Teigen said. "We're like, 'Ella Fitzgerald, that's such a pretty name!' We go back and forth on everything but this isn't our only baby so we're going to divide up the names."

Before Luna was born, Teigen said she "decided" to have a girl. In January, she told Entertainment Tonight she was having a boy next "for sure."

"Since this is coming up again, I said our next baby would be a boy because that is the embryo we have left. A boy. So. Yeah," she wrote on Twitter on Jan. 30.

Teigen announced they were expecting again in November. She showed off her baby bump the next day on Snapchat.