[3 examples of fetal genetic neuromuscular disorders which lead to hydramnion]

Causes of polyhydramnios include foetal neuromuscular disorders which cause inability of the foetus to swallow amniotic fluid. Three examples of such disorders are presented: X-linked myotubular myopathy, congenital myotonic dystrophy, and congenital nemaline myopathy. It is concluded that in case of polyhydramnios a search for foetal neuromuscular disease should be carried out. This implies ultrasound evaluation of the foetal movements, especially swallowing movements, neurological examination of the mother for myotonic dystrophy and examination of the newborn, which in selected cases includes muscle biopsy. Foetal neuromuscular disorders are usually genetic in origin. This adds to the need for accurate diagnosis and proper genetic counseling.