Can a 25lb Weight Gain Stretch out my Muscle Repair?

This is difficult to predict based on the pattern of your weight gain. IF you have an "apple" type body tendency to accumulate visceral fatty deposits, it is possible. If you have a pear like tendency, it s much less likely.

Given your dimensions, it is unlikely that a 25 lb weight gain will affect the muscle repair. However, the overall results including the contouring will be adversely affected. With weight loss, this will be reversible. There may be a permanent slight decrease in the tightness of the skin; that is, it may be slightly more lax.

In the unfortunate event that a patient gains weight after a tummy tuck, the result often suffers.   Unfortunately, if you gain intra-abdominal fat and stretch the overlying muscle/fascia repair, it is difficult to correct these changes without revision surgery.  However, if your changes are confined to the subcutaneous fat, you may be able to improve your result with diet and exercise.     

I would recommend following up with your plastic surgeon to determine how your result has been affected.   It is very important to maintain a stable weight after a tummy tuck or you may end up unhappy with your longterm results.

It is possible but unlikely. Best to See your surgeon to examine you. From MIAMI Dr. Darryl j. Blinski

Though 25 pounds is not a great weight gain, it is a significant amount to carry around, and if you tend to accumulate intra-abdominal fat you could jeopardize muscle repair. Your abdomen will respond to visceral or inside abdominal fat by relaxing and spreading the muscle. As weight is lost, just like after pregnancy, for some the muscle will not return to its original contour. Time to get serious about your investment and hit the gym.
Best of luck,
peterejohnsonmd