You will be advised if you have significantly ptotic (sagging) breasts, and it may be recommended that you undergo a breast lift with the implant.
Whilst on advice from the surgeon, you may choose to have implants anyway. (and you may be satisfied with the results) there is no guarantee that an implant alone will fill the breast enough. There is every chance that you may still need a lift.
You should prepare yourself for this, as having a second procedure requires financial consideration and further recovery – and generally would not be performed within 12 months of having had implants.