did they say your placenta is at the front? If so then yes there is a risk, if the placenta is lying behind your previous c section scar then it can potentially attach itself to the scar tissue, it’s called placenta accreta. A c section therefore becomes a little more complicated as when they cut into the scar they’ll be cutting the placenta which could cause bleeding.
With my second I was advised that my placenta was lying low behind my scar so I had to have additional scans in London to check the position at 32 and 36 weeks. I was advised that it was likely that the placenta will move up and away from the scar as baby grows, which thankfully it did.
if it had shown any sign of attachment then I was told I’d need to have an earlier c section at 38 weeks in UCLH with a specialist team and potentially a cut in a different location - it’s risky but as long as they know about in advance they can control any additional bleeding and make a plan to make you and baby safe. You can’t really tell what the situation will be now as the attachment (if it happens) won’t be visible on a scan until later.
it’s a worrying wait and I was googling a lot and they also dont explain it very well! But in the vast majority of cases the placenta does move up and away from the scar without attaching.
however it sounds like perhaps the midwife (or ultrasound tech?) was perhaps just mentioning it as a risk, as you’ve had previous c sections, and couldn’t actually see anything worrying at this point?
sometimes they can tell very early that the embryo has implanted to the c section scar, this is a different situation and is called a c section ectopic pregnancy. Sadly I think this puts the pregnancy at a much higher risk and is unlikely to progress… although it doesn’t sound like that’s what they saw. Wishing you the best!