Total antioxidant capacity and reactive oxygen species in amniotic fluid

To identify the presence and/or absence of reactive oxygen species and total antioxidant capacity in amniotic fluid and to determine changes in the levels of reactive oxygen species and total antioxidant capacity with advancing gestational age of pregnancy and fetal or neonatal weights.

Amniotic fluid was collected from a total of 26 nonsmoking patients. Nine specimens were collected in the third trimester of pregnancy, and 17 specimens were collected in the second trimester. Amniotic fluid reactive oxygen species and total antioxidant capacity levels were determined by chemiluminescence and spectrophotometric assays, respectively. Reactive oxygen species and total antioxidant capacity levels were established and then compared for advancing gestational ages and estimated fetal weights or neonatal weights.

Reactive oxygen species levels were present in some but not all specimens, and total antioxidant capacity was present in all specimens. Total antioxidant capacity but not reactive oxygen species levels increased from the second to the third trimester (347.0 mmol/L versus 776.0 mmol/L, P <.001). There was a positive Spearman correlation between total antioxidant capacity and gestational age (r = 0.72, 95% confidence interval 0.43, 1.0, P <.001) and between total antioxidant capacity and estimated fetal weights or neonatal birth weights (r = 0.70, 95% confidence interval 0.40, 1.0, P <.001). There was no correlation between reactive oxygen species and advancing gestational age or weight.

Total antioxidant capacity levels are present in amniotic fluid at least as early as the second trimester and increase with advancing gestational age and fetal or neonatal weights. Reactive oxygen species levels are not necessarily present in amniotic fluid, and they do not appear to be influenced by gestational age or estimated fetal or neonatal weights.