Effect of oxidative stress on birth sizes: consideration of window from mid pregnancy to delivery.

The aims of this study were to determine (1) whether the urinary mid pregnancy and placental delivery oxidative stress levels are related to the intrauterine condition and (2) whether long-lasting adverse oxidative stress is related to the birth size. We investigated pregnant women when they were at 24-28 weeks of pregnancy from October 2001 to May 2003 and at their delivery. Samples were obtained at each investigation time. Other information of mothers and their birth records were tracked from medical charts at Ewha Womans University Hospital in Seoul, South Korea. We quantified mid pregnancy oxidative stress by measuring urinary levels of 8-hydroxy-2'-deoxyguanosine (8-OHdG) and malondialdehyde (MDA) in 272 subjects. Intrauterine oxidative stress at delivery was measured by placental levels of 8-OHdG and MDA in 54 and 38 subjects, respectively. To identify the correlated intrauterine oxidative stress conditions, we evaluated kappa statistics and Pearson's correlations between maternal and placental oxidative stress. The relationships between intrauterine oxidative stress and birth sizes were examined by a general linear model. The levels of oxidative stress were divided to two groups based on their 75th percentile values. There was no correlation between urinary mid pregnancy and placental delivery oxidative stress levels for both MDA (kappa index=0.32, r=0.21) and 8-OHdG (kappa index=-0.13, r=-0.11). Both the urinary mid pregnancy and delivery 8-OHdG levels were significantly related to birth size. The birth size was largest in the 8-OHdG group. In addition, birth size was worse in the group with both high urinary mid pregnancy and placental oxidative stress than in any other combinations of low and high groups of urinary mid pregnancy and placental delivery oxidative stress. This evidence for a weak correlation between urinary mid pregnancy and placental delivery oxidative stress levels and its interactive effects on birth size suggest that the period from the middle to the end of pregnancy is critical window to intrauterine growth and also represents a modifiable period of the intrauterine condition. Therefore, applying interventions to pregnant women with high oxidative stress levels at midterm could contribute to increasing birth sizes.