Non‐protein‐bound iron and free radical damage in fetuses with rhesus haemolytic disease: influence of intrauterine transfusions

Objective To determine iron‐induced free radical damage in fetal rhesus haemolytic disease (RHD) before and after repeated intrauterine red blood cell transfusions and its relation to hydrops fetalis. Design Prospective, observational study. Setting Department of Obstetrics, Leiden University Medical Centre, the Netherlands. Population Fifty anaemic fetuses, including 13 hydropic ones, 9 preterm and 12 term neonates and 8 female non‐pregnant adults. Methods Venous blood plasma samples were collected from 50 fetuses suffering from RHD preliminary to the first, and if appropriate, subsequent intrauterine red blood cell transfusions for determination of iron status including non‐protein‐bound iron (NPBI) and iron‐binding primary antioxidant proteins, total plasma anti‐oxidant capacity and its contributing secondary antioxidants (e.g. vitamin C, uric acid, sulphydryl groups and peroxidation products). Results were compared with values of healthy preterm and term neonates directly at birth and adult controls. Within the fetal haemolytic group, 13 hydropic fetuses were analysed as a separate group. Main outcome measures Non‐protein‐bound iron, antioxidants, total antioxidant capacity and peroxidation products. Sub analysis of the outcome measures of the hydropic fetuses. Results RHD fetuses had at initial cordocentesis a significantly higher NPBI level and a significantly lower total plasma antioxidant capacity than control babies and adults. Their vitamin C tended to be more oxidised but lipid peroxidation had not increased, when compared with preterm babies. The repeated intrauterine red blood cell transfusions had a positive effect on the total antioxidant capacity of plasma and did not increase the concentration of NPBI. The hydropic fetuses, who had higher NPBI concentrations and lower plasma protein concentrations and total antioxidant capacity, did not show more peroxidation products in plasma than the non‐hydropic fetuses. Fetuses without reversal of hydrops despite intrauterine transfusions showed decreasing levels of proteins with subsequent transfusions but peroxidation products remained constant. Conclusion Repeated intrauterine red blood cell transfusions do not lead to free radical damage in the fetus in utero. Iron‐induced free radical activity does not appear to play a causative role in the proceeding of hydrops fetalis in RHD.