Morena Baccarin says she's ready to give birth any day now, and that welcoming her baby on Valentine's Day (or the day her new film, Deadpool, opens) would be the "best gift ever."

Baccarin looked absolutely radiant as she showed off her sizable baby bump in a little black dress at a fan screening of Deadpool at the AMC Empire Theatre in New York City on Monday.

The 36-year-old actress -- who walked the red-carpet with her Gotham co-star and boyfriend, Ben McKenzie -- opened up to ET's Carly Steel about her upcoming bundle of joy, and how close she is to going into labor.

"It might happen right now as we speak," Baccarin joked. "That'll be interesting, right?"

WATCH: Morena Baccarin and Ben McKenzie Plan to Marry

Despite how close she is to meeting her new baby, Baccarin revealed that she and McKenzie have yet to decide on a name.

"It's sort of hard until you see their little face, you know what I mean?" Baccarin shared. "So we have a list, but we'll wait."

She also revealed that the happy parents-to-be know the sex of their baby, but they aren't going to be sharing. At least they can narrow down what names to consider!

WATCH: Ben McKenzie and Morena Baccarin Make First Official Appearance as a Couple

Baccarin and her 37-year-old beau revealed that they were expecting their first child together in September, not long after going public with their romance. This will be Baccarin's second child after her son, Julius, who she welcomed with her ex, Austin Chick, in 2013.

Baccarin couldn't help but gush over McKenzie, and what it's like to work with her boyfriend on the set of their Fox drama.

"You get to go to work with the person you love every single day, and it's really nice," she shared. "I think we'd rarely get to see each other otherwise. So it's really fun."

NEWS: Morena Baccarin Shows Off Her Baby Bump While Filming Gotham With Boyfriend Ben McKenzie

In Deadpool, Baccarin stars opposite Ryan Reynolds, and the two have a rather extensive sex montage in the action-packed flick. Baccarin said she already warned McKenzie about the scene.

"He's used to it. He's a professional," said Baccarin, adding, "It was less about the sexiness of it, and more about the goofiness and the fun, you know?"

As for the cute couple's Valentine's Day plans, Baccarin said they're just "trying to get through tonight without [going into] labor," and then they'll starting thinking about how to celebrate the romantic holiday.

WATCH: Deadpool Star Ryan Reynolds Reveals the Most Romantic Thing He's Done For Blake Lively

ET also caught up with Baccarin's co-star, Deadpool himself, who admitted that he hadn't been able to make any Valentine's Day plans with his wife, Blake Lively. "But I will come up with something spectacular," Reynolds promised.

Check out the video below to hear more from Reynolds about the most romantic thing he's ever done for his loving wife.

Deadpool hits theaters Feb. 12.