When can I start sleeping on my side after under the muscle breast augmentation?

It's always best to ask your surgeon for his or her protocol. I advise my patients that they don’t
have to sleep on their back or sit up all night after breast
augmentation surgery. They can sleep any way they want from the night of
surgery on, including on their stomach, if they are comfortable enough.
They won’t pop or shift their implants by sleeping on them; implants
are extremely durable. For more information on this and
similar topics, I recommend a plastic surgery Q&A book like "The Scoop
On Breasts: A Plastic Surgeon Busts the Myths."

     In general, you should be able to sleep on your side after about 3-4 days, provided you are comfortable.  However, check with your plastic surgeon to best understand your surgeon's recommendations

Thank you for your excellent question.  As long as my patients maintain their augmentation in a well-fitting post surgical garment they can sleep on their sides the night of surgery.  At 7 days you should be able to but as each surgeon has their own recommendations based on your specific surgery it would be best to reach out to them to ensure you are okay to do so.  Hope this helps