Placental lead-induced oxidative stress and preterm delivery

It has been reported that impaired oxidant/antioxidant status is involved in a variety of pregnancy complications. To elucidate the possible free radical mediated mechanism of preterm delivery due to lead exposure by determining the placental lead level and oxidant/antioxidant status in women with the preterm and full-term deliveries. Twenty-nine women with preterm deliveries (gestational age 28-37 weeks) and 31 women with full-term deliveries (gestational age >37 weeks) attending a local hospital of Lucknow, India were recruited. Placental lead level, thiobarbituric acid reactive species (TBARS) level, as an end product of lipid peroxidation, antioxidant molecule glutathione (GSH) level, and activity of antioxidant enzymes; superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), and glutathione S-transferase (GST) were measured in the placental tissue. In the group with preterm delivery, significantly higher placental lead levels were recorded than in those of full-term (0.39μg/g vs. 0.27μg/g; p<0.05). TBARS was significantly higher while GSH was significantly lower in the placenta of women with the preterm deliveries as compared to the full-term deliveries (p<0.05 for each). Activity of antioxidant enzymes; SOD, CAT, GPx, and GR were significantly higher in the placenta of women having preterm deliveries than those of the full-term (p<0.05 for each). Furthermore, placental lead has significant positive correlations with TBARS (r=0.34, p<0.05), SOD (r=0.30, p<0.05) and CAT (r=0.41, p<0.05), and negative correlation with GSH (r=-0.31, p<0.05). There may be a number of plausible reasons for increased oxidative stress in preterm delivery. However, results of this pilot study suggest that lead-induced oxidative stress may be one of the underlying mechanism(s) of preterm delivery and emphasizes the importance of evaluating the impact of persistent environmental pollutants on adverse pregnancy outcome.