Increased Risk in Combining Tummy Tuck and Breast Lift?

It is always safer to perform smaller operations, so combing two large procedures does increase the risks. In my mind, the most serious increased risk of combining the two procedures is that the possibility of venous thrombosis and pulmonary embolism increases with longer surgical times. That being said, operations lasting less than 6 hours are relatively safe, and combining a tummy tuck with a breast reduction is quite common. Speak with your individual surgeon to review the risks and ask how long it would take them to perform the combined procedure.
Dr.B

We combine Tummy Tuck and Breast Lift (Mastopexy) with or without implants all the time in our practice in Memphis. This commonly done combination procedure falls under the grouping of cosmetic procedures known as MOMMY MAKEOVER operations.
All things being equal, assuming you have no preexisting health issues, the only real determinant of surgical risk is the duration of the procedure , in other words, time in the OR. The longer the procedure, the higher the risk of blood clot formation in your veins and the higher the chance of these clots going to the lungs (IE pulmonary emboli). Most board certified Plastic surgeons are very aware of this and take precautions to reduce this risk.
I hope this answers your question.