Complications and problems can occur following any operation. If you are considering breast reduction surgery, you should think about the following complications:
Surgical complications
Haemorrhage, haematoma, (chronic) pain, infection, seroma, need for further surgery, risk of anaesthetic, DVT/PE
Scarring & healing
Hypertrophic/keloid scar, hypo/hyperpigmentation, itching/tender scars, dog ear, wound breakdown, delayed healing, poor healing, flap necrosis, nipple necrosis, loss of nipple sensation/contractility, inability to breast feed, difficulty with interpretation of future mammograms
Cosmetic complications
Bottoming out, sunrise nipple, asymmetry, fat necrosis, unable to guarantee a particular cup size, failure to improve symptoms (including back/shoulder/neck pain), late shape change, dissatisfaction with appearance
This is not an exhaustive list but it is intended as a starting point for complications you may wish to discuss in more detail with your surgeon.