Sometimes such extreme unfortunate things happen without any clue. Diabetes
, autoimmune diseases, thyroid
abnormalities, intrauterine infections, trauma, cord accidents, all are associated with such incidents. Also we don't know if the baby had some congenital anomalies. Still unexplained IUD is a reality.
But one thing strike me. A baby with good movements (?? didn't someone check the FH then?) getting macerated in 48 hrs is quite unlikely. This might be a clue for your investigation.
In this kind of situations,never put the blame on the subject (patient). It is gross. Fetal movement
is such an unreliable indicator that almost every women claim to have it till hours or minutes before the diagnosis of IUD.