It's one of the most jarring, life-changing moments for any woman faced with the decision.
In her new book, Sorry Not Sorry, Naya Rivera got candid about her 2010 abortion, and why she chose not to tell the father, now-husband Ryan Dorsey, until a few years later.
"I think it's always on your mind, and it's one of those little scars in life," Rivera told Entertainment Tonight.
"When I was writing the book, it was really important for to include that, because this is ... a part of my story and a part of who I am.
"And like I said, the statistic is crazy -- there are so many women out there that are going through this and nobody gets to talk about it."
Rivera compares the feeling of realizing she was pregnant at 23 to learning of Glee co-star Cory Monteith's July 2013 death.
"It was kind of that same feeling when I had the call about Cory. It was like the world stops, and you kind of black out for a minute," she recalled.
"And you are like, 'What is going on? I have all this other stuff to do, you know?' So it was just never a real question."
Rivera went on to date Mark Salling and Big Sean, but eventually got back together with Dorsey, 33.
The couple married in July 2014, and their son, Josey, turns 1 on Saturday.
Rivera didn't tell Dorsey about the abortion until a few years later, but his reaction is the reason why they ended up together.
"That was really nerve-racking," Rivera recalled.
"I didn't know how he would react, obviously. It had been so many years.
"He ended up saying, you know, one of the best things that any man in that situation could have ever said.
"And I think that it's just a true testament to him and us, and I'm grateful for where we are now."
In the back of her mind, Rivera always knew Dorsey was the one.
"I have always kept a flame for him," she revealed, despite their 2010 break-up.
"In between boyfriends or whatever, if I was single for a minute, I would always answer his emails and go see him. He was just kind of always the One."
Does Rivera still think about the abortion?
"Absolutely," she answered.
"Like I said, it's something that is one of life's little scars that you get along the way, and the scars are never really healed.
"They are always kind of still there -- they are just not bleeding anymore."