Looking back on her decision to try IVF with her husband Aaron Lohr, she admits they originally weren't planning on having children.
But things changed when Aaron got to know Idina's 13-year-old son Walker, whom she shares with ex Taye Diggs.
"Maybe before meeting me, [Aaron] didn't think he wanted to have kids, and then, he sees how good of a dad he can be," Idina told People. "So, I wanted that for him."
In the documentary, Idina chronicles the difficulties of traveling from venue to venue while also balancing her IVF doctor's appointments and spending time with her family.
"I'm literally going through stuff that I'm shooting into my body, and I don't know how that's going to affect my voice," she says in the documentary.
She continued, "And it may force me to make extra trips to get back and forth to the doctor in addition to making trips to get home to my family. And all of that isn't great on your body when you're trying to have a baby."
Reflecting on her choice to share some of her most "emotional" and "physical" moments in the film, Idina says she wanted to help others going through the same thing.
"No matter what the outcome, I just wanted women to feel seen in this film and people to understand what we go through. It was important to me to forgo the privacy of that and allow people to have a little window into that experience,” Idina said.
Ultimately, Idina and Aaron realized that having another child "wasn't meant to be" and have "moved beyond that."
"I think going through all that, you're so exhausted by it that finally, it becomes apparent like, 'I don't want to do this anymore, and it just wasn't meant to be,' and you're resolved in that," Idina shared.
She noted that Aaron "feels really loved that I even tried and put my body through that."
And at the end of the day, Idina says she's very "fortunate" to have her son, Walker, whom Aaron sees as his own child now.
"I have this amazing son, and I was fortunate enough to have him. And the pregnancy was pretty easy, and I conceived easily, and there’s a lot of people that don’t even get to have that," Idina said.
"I think we feel content and lucky with what we have," she concluded.
Idina Menzel: Which Way to the Stage? premieres December 9 on Disney+.