BBL 12 days post-op. Can I expect it to shrink considerably?

You will lose 50% or so of the fat that is transferred.   Some patients retain more and some retain less.

Thank you for your question. There will be significant changes over the next several weeks to months. You will likely see some settling and absorption of the grafted fat over time. I would suggest you wait until at least 3-6 months until the final results are revealed. Discuss your concerns with your surgeon as things proceed.Best of luck!

Dear 12312345123,I understand that you are worried about the size of your buttocks. However, you are still in the early phase of the recovery period. Please do allow some time for the healing process to occur. If after a 4-6 weeks, you are not satisfied with the appearance, you can visit your plastic surgeon and discuss your concerns.Daniel Barrett, MD, MHA, MS 
Certified, American Board of Plastic Surgery  
Member, Am. Society of Plastic Surgery

Thanks for posting. Your buttocks will change during the first few months. There are two reasons for this: 1st is swelling. Swelling is extra fluid in your tissues. It occurs immediately after surgery and resolves over weeks. 2nd is fat resorption. In BBL, somewhere around 60-70% of the fat that is transferred stays permanently and this occurs over the first 4-6 months. So, it is common practice to make the buttock larger than is planned, knowing the size will go down a bit. BBL is a great procedure because it can be customized to your desired size. It's important to have a clear conversation with your surgeon about your size and shape goals.