Fat transfer breast augmentation cause sagging in the future?

Over time and with breast feeding, your breasts will change. The larger the breast, there is more chance of sagging. With weight gain, fat transfers can also grow larger, and the reverse is true with weight loss. Fat transfers only need to be repeated if you desire more volume. Not all fat cells transferred will stay over time.

or your breasts for that matter.  Aging will allow your breasts to sag as does breast feeding and weight loss and the weight of implants.  Fat grafting shouldn't be counted on for large enhancements (perhaps a cup size).  And whatever fat is used in grafting will still act like the fat where it came from so tummy fat will gain size as you gain weight and lose it last when you lose weight.  Fat grafting should be used for volume enhancement and for filling in any small defects.