Jade announced the big news via Instagram on Tuesday night, before The Bachelorette host Chris Harrison revealed Jade and Tanner's baby had been born during the season finale of Hannah Brown's season.
"I accidentally gave birth at home last night, in our master closet. I've been still processing the shock of this all, as this was not all at what I had planned, but I am so so thankful for each person who helped bring our son into the world safely," Jade captioned a photo of herself holding her son in the closet.
"I'll share my whole birth story soon, but long story short, my waters broke and 75 minutes later I gave birth to our healthy baby boy while clutching a bench in our closet."
"It was one of the scariest moments of my life because I felt so out of control, but Tanner, Tanner's mom, my mom and the medics and firefighters kept me going when I felt like the world was caving in on me and my unborn baby."
Jade added, "I was going to share the happy, cute Instagrammable pics first, but this felt right to me. So incredibly grateful for the support system we had and for this beautiful boy I get to hold in my arms."
Tanner toldPeople he and Jade are "over the moon" about the new addition to their family, which includes daughter Emerson "Emmy" Avery, who turns 2 on August 17.
"We are over the moon for our little guy. He came into this world fast at 7 lbs., 9 oz and 20 in. long," Tanner said in a statement.
"Mom and baby boy are doing great. Emmy just met her little brother -- she greeted him with a kiss on the head, so I guess that means she will allow us to bring him home! We are officially a family of four!"
Jade announced she and Tanner were expecting Baby No. 2 on Instagram in late January, sharing family photos at the beach in which Jade was holding up a strip of ultrasound photos.
"Baby #2 is adding to our crew!! We are overjoyed our bundle of love will be joining us in August!" Jade wrote at the time. "We've been dreaming of you for a while now, and you are already loved beyond imaginable, sweet baby."
Prior to the announcement of their second child's gender, however, Jade opened up in February about how she had sadly suffered a miscarriage during her very first pregnancy.
"I had a miscarriage. These words have burned inside me for over three years. I was honestly so scared to share our story, because I have always had this inner voice that's said I don't matter as much... My journey with my grief has been a rollercoaster," Jade shared at the time, adding that the baby was conceived during the couple's stint on Bachelor in Paradise.
"I've also been afraid to tell people Tanner and I got pregnant on Bachelor in Paradise while filming. I've been keeping this weight for a long time."