Thank you for your question. It is impossible to answer your question without at least a photograph. You will need examination by your plastic surgeon to enhance your question fully. It is not uncommon for the chest to be quite swollen after breast implants but if the skin is detached from the breast bone and you can push your implants to the center and they meet and touch then you may have symmastia.
If the implant is larger than the available skin envelope then the skin will raise early after augmentation. Symmastia occurs if the pocket tears or shifts allowing the implants to run together in the middle. Pressure over the breast bone with additional padding in your bra might help as the skin envelope begins to relax.
Your description of “skin in between my breasts is slightly raise” does not sound consistent with symmastia. Unfortunately, there is no way of getting ahead of this potential problem, if it were to arise. You may wish to discuss the use of a “symmastia bra” with your plastic surgeon; this "bra" applies pressure to the sternal area. Its use may, at least, give you some peace of mind. I hope this, and the attached link devoted to symmastia correction ( also demonstrates the use of the bra) helps.
Your description of the early results of your breast augmentation procedure sound more like swelling and not symmastia. It is very common to have swelling that crosses the sternum in the early period after breast augmentation surgery.
Following breast augmentation, post operative swelling can
certainly involve the skin and soft tissues over the sternum. But this swelling
does not represent synmastia. Synmastia is when both breasts meet/touch in the
midline; it is more common when large implants are used. Following subglandular
augmentation, this would occur immediately following surgery if the pockets were
dissected too far medially on both sides; or it could occur in a delayed
fashion if the medial pocket dissection was in close proximity and then stretched
or tore, allowing the implants to move together in the midline. Following a subpectoral
augmentation, synmastia is less likely to occur because the implants are placed
below the muscle. However, if significant release of the medial muscle origins
was performed, the implants could move medially and synmastia it could develop.
Synmastia is usually a problem that would require surgical correction.
The fact that you describe "the skin in between my breasts
is slightly raised and I can push it down to my sternum" would suggest
that there is a space between the implants.
Swelling between the breasts will improve with time. If you
would like this to improve more quickly, then the use of some additional
pressure/compression in the sternal area would be helpful.
Best wishes. Ken Dembny