Excess amniotic fluid that surrounds the baby is one clue in diagnosis of myotonic dystrophy. This causes preterm labor and potential severe issues in the children. This study looks at cases of unknown polyhydramnois and concluded that 9.7% of this population that was studied had DM
Myotonic dystrophy is a significant cause of idiopathic polyhydramnios.
Source
Department of Obstetrics and Gynecology, University of Utah School of Medicine, Salt Lake City 84132, USA.

here are now quite a few different ways that myotonic dystrophy can be defeated. To the left is the pathway that the FDA requires and the most advanced pathways are still in animal studies. This is a nice article but technical.