Graham - who is known for being a proponent of body positivity - had to "reimagine" her relationship with her body during pregnancy, and felt "devastated" by her stretch marks at first.
But the beauty soon realised her marks were not "battle wounds", and learned to "celebrate" her "new body".
The model - who is married to Justin Ervin - added: "And then, when I got pregnant, I had to reimagine my relationship with my body with this creature inside me taking over. I was gaining weight so rapidly. Then, to get stretch marks on my stomach, that to me was like, 'Oh my gosh. I can't believe this happened.' At first it felt devastating, and then when I met Isaac, I said, 'No, this is exactly what every woman has talked about for ages. This is not just a battle wound. This is something that has changed my life forever, and I'm going to celebrate my new body.' "
Graham also spoke about her decision to stop letting the fashion industry "take over" her body.
Speaking to her pal Kristen Bell in an interview for the first ever digital edition of ELLE magazine, she said: "I let the fashion industry take over my body for too many years. The moment I stepped free and said, 'Enough is enough - I'm going to do what I want,' is when I started seeing changes, not only in my personal life but in my professional life. But it really takes hard work."