She said on Sunday, "I'm sorry for keeping you in the dark through all the assumptions. I understand you're used to me bringing you along on all my journeys. My pregnancy was one I chose not to do in front of the world."
The youngest Kardashian-Jenner sibling gave birth to a healthy girl on February 1.
Check out her Instagram post here:
"I knew for myself I needed to prepare for this role of a lifetime in the most positive, stress free, and healthy way I knew how. There was no gotcha moment, no big paid reveal I had planned. I knew my baby would feel every stress and every emotion so I chose to do it this way for my little life and our happiness," she added.
The newborn is her and rapper Travis Scott's first child.
"Pregnancy has been the most beautiful, empowering, and life-changing experience I've had in my entire life and I'm actually going to miss it. I appreciate my friends and especially my family for helping me make this special moment as private as we could. My beautiful and healthy baby girl arrived February 1st and I just couldn't wait to share this blessing. I've never felt love and happiness like this I could burst! Thank you for understanding," her post read.
The reports of her pregnancy surfaced in September but Jenner dismissed it and stayed away from social media since then.