I heard a good news article on unexplained miscarriages on NPR last week.
There’s a correlation between having a healthy baby and the volume of the placenta. Small placentas result in loss.
Which makes sense, the placenta is passing all the oxygen and nutrients to the baby, if it fails to size up, the baby is starved of nutrients and… well…
The doctor who invented the process to measure placental volume is getting the usual pushback from established medicine though. :(