I had a 17 week loss last summer. I didn't know until my Dr appt and the US showed that he had just past since he was measuring right where he was suppose to. We still don't have a definite answer as to what happened as when he was born, he was perfectly formed and didn't show any signs of a defect. When I met with the perinatal Dr for this pregnancy, he explained that most likely our son passed from a chromosomal issue that happened after the 1st cell divide which would be why he appeared normal looking. I still don't know for sure what happened and probably never will this side of eternity.