The underarm incision is less common today than it once was, when implants were typically saline-filled. As silicone breast implants have become more widespread, the inframammary incision (in the crease of the breast) and periareolar incision (on the bottom half of the areola) have come to prevail.
With an inframammary incision, ideally the scar will be invisible under the bra even with your arms raised. This type of incision allows good access for the surgeon to place the implant under the mammary gland or under the muscle. Possible drawbacks include poor visibility if an implant needs to be replaced and persistence of the scar if the patient has a breast lift in the future. Special “insertion sleeves” can be used to make the already short scar even shorter.
Periareolar access places the incision on the lower half of the darker skin of the areola and lighter skin of the breast. This is considered the least visible scar from an aesthetic standpoint. Limiting factors are the diameter of the areola and chosen implant size. Implants can usually be replaced through the same incision. Another advantage is that the scar can be removed in a future breast lift.