No idea, but I was told it was fine that the placenta was breaking down and calcifying at 37 weeks. Just that they needed to keep an eye on it to make sure it didn't speed up. My son was evicted at 42 weeks. He was perfectly healthy but did have some signs of post-maturity. (Though I wouldn't think that would be that uncommon with a 42 weeker). My daughter was born at 41 weeks and the placenta aged much slower than it did with my son. She was a larger baby than he was so I don't know if the baby's size puts more demands on it or not. (She was 11lbs 4oz. My son was 10lbs 8oz).