Hello, It would not be normal for you to gain weight after a blood transfusion or an abdominal surgery. If the weight gain happened over the course of just a few days, I would suspect that it was possibly from fluid retention, which can sometimes happen with a blood transfusion as well. I would have expected the fluid to have come off over the course of nine months, but if there is some problem with your heart or another reason for your body to not be able to get rid of excess fluid, you may still have this edema. However, this would usually be noticeable to you, especially in your legs. There would be no other causes of weight gain in a very short amount of time other than fluid retention. Otherwise, it may be that you have gained weight gradually over time. Perhaps after the surgery your diet or lifestyle changed in such a way that you gained weight. Over time our metabolism changes and that may have contributed as well. Hope I have answered your query. Let me know if I can assist you further. Regards, Dr. Aaron Branch, General & Family Physician