One of my girls lost a litter in 2004, she was scanned at 5 weeks we clearly saw 7 live healthy pups, at 7 weeks she aborted 5 no signs of the other two which we presume were reabsorbed. She was scanned after aborting and was completely empty.
Almost ditto Sharon's story, except at the re-scan there was still some debris on my girl and she was subsequently very ill with infection and had to be speyed.