Hailey Bieber Says Baby Jack Was a Surprise

Hailey Bieber's proof you should "Never Say Never" when it comes to pregnancy ... because she was pretty sure she wasn't going to be carrying a baby for awhile -- until she became pregnant with Jack!

The model and beauty mogul revealed Jack wasn't a planned pregnancy on the "SHE M.D." podcast -- cohosted by Dr. Thais Aliabadi and women's advocate Mary Alice Haney -- because she had a septum in her uterus.

For the uninitiated ... a uterine septum is a membrane which divides the uterus into two separate and distinct parts -- and causes a higher risk of miscarriages, infertility and preterm labor.

Bieber says Dr. Aliabadi told her not to get pregnant while they worked on a treatment plan for the septum ... and yet, shortly after that convo, Hailey says she got knocked up.

Dr. Aliabadi admits she wasn't thrilled for Hailey at first because she was worried about her health ... but, everything ultimately worked out fine -- and Jack was born in August 2024.

The two Bieber's have shared photos and videos of Jack over the years ... and Justin Bieber even mentions Jack on the album "Swag II."