Pregnant after tummy tuck, will delivery via C-section damage the muscle repair?

Dear Peaceful1666,
it is hard to tell for sure, but your body will most likely change during pregnancy and c-section. You can always get a revision surgery after delivery.
Daniel Barrett, MD
Certified, American Board of Plastic Surgery
Member, American Society of Plastic Surgery
Member, American Society of Aesthetic Plastic Surgery

As less Weight changes during the pregnancy the abdominal stretching have lesser changes ( loose skin or weak muscles)
As you are pointing in your question the best for maintaining your tummy tuck results is to try to control weight gain and this should done on a healthy way under the supervision of a OB/GYN. Nothing to be worry about for the c-section and the muscle repair , this will no affect it.