The model has been documenting her current journey to motherhood on social media and on Monday (06Jun16), the 28-year-old took to Snapchat to share a video of herself snacking in the kitchen, admitting she wants to pack on the extra weight just so she could challenge herself to slim down following the baby's birth.
"My goal is to gain 100 pounds this pregnancy," she said in the clip. "I'mma (I'm gonna) tear it up, and then I'mma snap back (sic)."
Blac then posted another video, in which she tips the scales at 165.6 pounds (75 kilograms), explaining, "Before I got pregnant, I was about 139 (pounds)."
The star will have her work cut out for her when it comes time to shed the extra baby weight, but she will be able to turn to Rob's sister, Kim Kardashian, for advice after the reality TV beauty successfully shed the 52 pounds (23.6 kilograms) she gained while pregnant with her second child, son Saint, who was born in December (15).
Meanwhile, Blac, who has a three-year-old son, King Cairo, with her rapper ex Tyga, previously told fans she was really enjoying her second pregnancy.
"If you guys are wondering, I'm actually having a really good pregnancy similar to King's," she detailed in a video uploaded last week (ends03Jun16). "No morning sickness, no cravings - just baby."
Blac and Rob announced they are expecting their first child together last month (May16), just weeks after confirming their engagement in April (16).
They are currently keeping busy filming their own six-part docu-series, tentatively-titled Rob & Chyna, which will air on America's E! network later this year (16). They will also shoot a TV special after their child is born to update fans on their family life.