THE ROLE OF DEOXYRIBONUCLEASE-I IN AMNIOTIC-FLUID DURING PREGNANCY AND LABOR

The purpose of this study was to detect the presence, and determine th e normal values and the significance of DNase I in the amniotic fluid and in human placentas. Fifty-one pregnant women at 16-22 weeks of ges tation and 89 women in spontaneous labour at term were recruited to th e study. DNase I activity was measured in amniotic fluid and cytoplasm ic extracts from the fetal portion of placentas by using a spectrophot ometric technique (DNA precipitation assay) and nucleic acid electroph oresis, following degradation of the DNA by the enzyme. DNase I activi ty was undetectable in the placental cytoplasmic extracts. In the seco nd trimester of pregnancy DNase I activity was detectable in amniotic fluid (2.3+/-0.64x10(5) U/l). During labour DNase I activity was also detectable, but reduced levels were observed in the presence of clear amniotic fluid, compared to second trimester levels, (1.9+/-0.44x10(5) U/l, P<0.001), whereas higher levels were found in the presence of me conium-stained amniotic fluid compared to both second trimester and cl ear amniotic fluid at labour (11.4+/-4.1x10(5) U/l, P<0.001 and P<0.00 1, respectively). Three out of 17 fetuses with meconium-stained amniot ic fluid (18%) developed perinatal infection. In conclusion, the detec tion of DNase I activity in the amniotic fluid of second and third tri mester indicates a physiological role in human pregnancy. DNase I acti vity normally decreases at term, compared to second trimester levels, but increases significantly in the presence of meconium. (C) 1998 Else vier Science Ireland Ltd.