Intrauterine detection of cystic fibrosis.

Thirteen pregnancies of obligate heterozygotes of cystic fibrosis have been prospectively monitored utilizing quantitative and qualitative measurements of methylumbelliferylguanidinobenzoate (MUGB) reactive proteases in amniotic fluid. In each case the diagnosis was accurately ascertained in midtrimester and confirmed after delivery. The measurement of MUGB reactivity in midtrimester amniotic fluid by three different procedures, quantitative analysis, polyacrylamide isoelectric focusing, and column filtration appears to provide a practical and reliable approach for the intrauterine detection of cystic fibrosis.