The 24-year-old daughter of Sarah Palin made the announcement on her Patheos blog Thursday.
"(I'm announcing this news a lot sooner than I ever expected due to the constant trolls who have nothing better to talk about!!!). I wanted you guys to be the first to know that I am pregnant," the two-time Dancing with the Stars contestant wrote.
This news comes about a month after Bristol announced she and her ex-fiance Sgt. Dakota Meyer, a 26-year-old U.S. Marine veteran who had received the Medal of Honor in 2009, had called off their engagement. Bristol had taken everyone by surprise when she canceled the wedding just days before she was set to walk down the aisle and offered a very vague explanation.
"Honestly, I've been trying my hardest to keep my chin up on this one. At the end of the day there's nothing I can't do with God by my side, and I know I am fully capable of handling anything that is put in front of me with dignity and grace," Bristol continued.
"Life moves on no matter what. So no matter how you feel, you get up, get dressed, show up, and never give up. When life gets tough, there is no other option but to get tougher. I know this has been, and will be, a huge disappointment to my family, to my close friends, and to many of you."
Bristol already has a son, Tripp Easton Mitchell Johnston, from a previous relationship with ex-fiance Levi Johnston. They welcomed Tripp in December 2008 when Bristol was only 18-years-old, and then she became a teen pregnancy prevention spokesperson.
Bristol and Johnston had been engaged twice before officially calling it quits in 2010. Johnston now has a daughter, who was born in September 2012, with his wife Sunny Oglesby.
"Please respect Tripp's and my privacy during this time. I do not want any lectures and I do not want any sympathy," Bristol concluded in her blog. "My little family always has, and always will come first. Tripp, this new baby, and I will all be fine, because God is merciful."
Bristol declined to reveal who is the father of her second baby. She provided no further details.
Bristol competed on the eleventh season of Dancing with the Stars back in 2010 and reached the finals with pro partner Mark Ballas, finishing in third place. In November 2010, she appeared on TLC's Sarah Palin's Alaska documentary.
Bristol then starred in Bristol Palin: Life's a Tripp on Lifetime in Summer 2012. She most recently competed on Dancing with the Stars' Fall 2012 All-Stars edition. She was sent home in the fourth week of the fifteenth-season competition.