How can I get rid of loose sagging skin after pregnancy?

The first step after pregnancy is to determine if you are done with children, and about 6 months done with breast feeding.  You want to avoid possibly having to redo your breast surgery if you become pregnant right away!

Next, what breast size is necessary?   If a larger size is needed, an implant is indicated to bring you up to the size you need to have.

Last, the distances you have from the breastplate to the nipples will give a good indication of whether or not a lift is needed, and if so what type of lift.  Avoid getting a really large implant to overcome droopiness; this may just leave you with large breasts with a low positioned nipple-areolar complex.

This is a straightforward triage system that treats loss of volume with an implant and droopiness with a lift.

Many artistic decisions go into the surgery itself, of course, such as how much tension is put on the incisions, which breast lift techniques are used, how the breast is shaped, etc. 

Also, when both an augmentation and a lift are done at the same time, you might put pressure on the blood supply to the nipple.  When both procedures are performed together, it is extremely important to select a surgeon with a great deal of experience in determining "how much" is safe.  A skilled surgeon minimizes bad scarring and nipple-areolar disasters by not exceeding the ability of the tissues to supply blood to the operated areas.  In some high risk cases, such as a previous above the muscle implant, it may be better to stage the surgeries.