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
Am J Obstet Gynecol. 1998 Oct;179(4):974-7.
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.