Prenatal diagnosis of cystic fibrosis by methylumbelliferylguanidinobenzoate protease titration in amniotic fluid.

Amniotic fluids were obtained from 19 mothers who had previously given birth to a child with cystic fibrosis. Measurement of methylumbelliferylguanidinobenzoate (MUGB) reactive proteases suggested that all 19 would have unaffected babies. Amongst the first 10 cases to come to term there were 5 infants with cystic fibrosis. It is concluded that MUGB protease titration is not suitable for the early prenatal diagnosis of cystic fibrosis.