DS was a complete breech throughout the entire third trimester and I had a C-section when my water broke at 37+1. I had a UP with DD, so I didn't have late ultrasounds, but I could have sworn I felt her head when I checked my cervix a couple of days before she was born. She ended up moving into footling breech and I had an emergency C/S under general when my water broke on my due date.
I had a saline sonogram when I was going through my infertility treatment and my RE said my uterus looked perfectly normal. There were no abnormalities noted during either C/S. With DS's pregnancy I was working a desk job, so I spent a lot of time sitting with my feet up. But with DD, I was very much on my feet, especially in the last trimester, up until a month before she was born. So I can't think of anything similar between the pregnancies that would cause both to remain in breech position.
Any thoughts as to what might have caused this? A third pregnancy is highly unlikely, but if it did happen, I'd like to go for a VBA2C, but obviously that won't be possible with another breech.