The answer to this question actually may depend on what year you are asking it. If you asked this question in 2017 then the answer would be a very loud ‘yes’, but in 2021 the answer may surprise you.
When surgeons first started placing breast implants in women they placed the implant right under the breast gland, but there were lots of problems. Sometimes the implants would look really fake as you could see the whole implant under the skin. Other times the breast would have lots of rippling on the outside of the breast and sometimes in the cleavage area as well. Capsular contracture was a big problem with the tissue around the breast implants becoming very hard and distorting the breast. Sometimes the implants would even work their way through the skin.
So there was a movement to change the location of the implants to minimize these problems and surgeons began placing the implants under the pectoralis major muscle which sits under the breast. This way there was more coverage of the implant with more tissue and it minimized the implants looking fake, prevented some rippling, and stopped implants eroding through the skin. The breasts looked a little different because the muscle had prevented the implants from being as low as they should be to be right under the breast. So surgeons kind of compromised and started to divide the muscle, that is, cut the bottom part of the muscle to allow the implants to drop down to a better position—making them look a little more like they were under the breast.
Then over the last several years plastic surgeons, learning a lot from reconstruction of patients breasts after they have been removed because of breast cancer and taking advantage of the newer implants, have gone back to placing the implants directly under the breast. The results are impressive as the breasts look natural, and beautiful as the implant is in a position where it should be—directly under the breast. This became possible because the newer gummy bear implants don’t have all of the problems of the implants of the 1970s, and other techniques like fat transfer have allowed surgeons to place the implant directly under the breast.
There are still patients who because they are very thin and therefore don’t have enough tissue are better candidates for placing the implants under the muscle, but for those patients with adequate breast tissue more and more plastic surgeons prefer to place the implants under the gland.