Pregnant Naomi Osaka Says She Learned Sex of Her Baby But Partner Cordae 'Doesn't Know' Yet

Cassy Athena/Getty Cordae and Naomi Osaka at the WBA World Lightweight Championship title

Naomi Osaka is getting ready to be a mom!

Speaking with PEOPLE about her partnership with Victoria's Secret at an event in West Hollywood Tuesday, the pregnant tennis pro, 25, opened up about preparations for her upcoming arrival.

"I've been preparing, but he doesn't know the gender yet, only I know," Osaka reveals to PEOPLE, referencing boyfriend Cordae. "So it's not like I can build out the room or anything."

Osaka continues, "So I don't know, [I'm] just kind of winging it. That's kind of the key motto in my life a little."

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Robert Prange/Getty; Naomi Osaka/Instagram

RELATED: Naomi Osaka Is Pregnant! Tennis Star Is Expecting Her First Baby with Boyfriend Cordae

Osaka has been enjoying her pregnancy thus far, dressing in plenty of comfy loose button-downs from her Victoria's Secret collaboration. The collection — available now in stores and online — offers robes, rompers, sleep shirts and shorts in a variety of pastel lavenders, light jades and muted pinks.

"I've been wearing this a lot, almost every day. It's very comfortable, so I'm very glad about that," she says of the pieces, which she designed and curated.

"I think the button-down shirts, which I'm wearing right now. It's great as a relaxation. It's great as a pajama. And also to go outside, you can also just wear it as a shirt."

Victoria's Secret Naomi Osaka

Osaka is especially looking forward to two things in the next year: the birth of her little one and her return to the tennis court.

"I think what I'm looking forward to most is the challenges and just learning," Osaka says of motherhood.

Victoria's Secret Naomi Osaka

"I think there's going to be a lot of things that I don't know, but I have a lot of really amazing people close to me that I can ask questions about. Just a new adventure."