Amniotic immunoreactive trypsin in pregnancies with normal and pathological outcomes.

Immunoreactive trypsin (IRT) has been studied in amniotic fluid as a possible complementary test substance for the prenatal diagnosis of cystic fibrosis (CF). 219 normal amniotic fluids have been tested in order to establish the normal ranges from 14 to 40 gestational weeks (g.w.). The IRT level increases from g.w. 14 to 19, remains stable from g.w. 19 to 25 and then decreases rapidly to low levels. A retrospective study of 4 presumed CF fluids, as determined by abnormal alkaline phosphatase levels, showed decreased IRT values in 3 out of 4 fluids. The difference between the mean value and the normal mean was not significant. The prospective study allowed us to test 2 fluids from pregnancies affected by meconium ileus. IRT level was highly elevated, 530 times the normal mean value at g.w. 34 for a non-CF fetus and 18 times the normal mean value for a CF fetus at g.w. 31. In 4 out of 5 cases of fetal severe intra-uterine growth retardation, IRT levels appeared mildly elevated. Other abnormalities are reviewed.