School of Public Health, Seoul National University, Seoul, Republic of Korea.
School of Public Health, Seoul National University, Seoul, Republic of Korea; Institute of Health and Environment, Seoul National University, Seoul, Republic of Korea; Chemical Safety Research Center, Korea Research Institute of Chemical Technology, Daejeon, Republic of Korea.
Environ Res. 2021 Jul;198:110473. doi: 10.1016/j.envres.2020.110473. Epub 2020 Nov 13.
Due to dilution status of the urine, chemical concentrations measured in spot urine are frequently adjusted using correction factors, such as creatinine, specific gravity (SG), or osmolarity of the urine. Urinary correction factors, however, can be influenced dramatically by physiological changes such as pregnancy. Details about the variation of urine dilution over the course of pregnancy are not well characterized. In the present study, we investigated the variation of urine correction factors over time among the pregnant women of Korea (n = 69) and Thailand (n = 102). Creatinine, SG, and osmolality were determined in the urine samples obtained in each trimester of the participating women, and were compared by sampling time and by nationality. Implication of the variation in these correction factors was studied using phthalate metabolites measured in the urine samples as model chemicals. Urinary correction factors significantly varied across the trimesters especially in Korean pregnant women: urinary creatinine and osmolality were significantly lower in the third trimester (T3) urine than the first trimester (T1) urine. Urinary creatinine and SG of the T3 urine of Korean pregnant women were also significantly lower than those reported from the non-pregnant women who participated in Korean National Environmental Health Survey (KoNEHS) 2015-2017. Among Thai women, however, these correction factors were rather stable across the pregnancy. Differences in ethnicity, or in behavior such as water consumption amount may partly explain the differences. Temporal changes in these urine correction factors influenced the urinary phthalate metabolite concentrations adjusted for dilution, in both Korean and Thai pregnant women. The present observations show that the variations of urinary correction factors should be considered in exposure assessment of urinary chemicals for pregnant women, in order to circumvent potential bias due to physiological changes occurring during pregnancy, and to reduce errors in exposure classification and association.
由于尿液的稀释状态，通常使用校正因子（如肌酐、比重或尿液渗透压）来校正尿液中测定的化学物质浓度。然而，尿液校正因子会受到妊娠等生理变化的显著影响。关于妊娠过程中尿液稀释变化的详细信息尚未得到很好的描述。在本研究中，我们调查了韩国（n=69）和泰国（n=102）孕妇尿液校正因子随时间的变化。测定了参与女性每个孕期的尿液样本中的肌酐、比重和渗透压，并按采样时间和国籍进行了比较。使用尿液样本中测量的邻苯二甲酸代谢物研究了这些校正因子变化的影响，这些代谢物作为模型化学物质。尿液校正因子在整个孕期差异显著，特别是在韩国孕妇中：第三孕期（T3）尿液的肌酐和渗透压明显低于第一孕期（T1）尿液。韩国孕妇 T3 尿液的肌酐和比重也明显低于 2015-2017 年参与韩国国家环境健康调查（KoNEHS）的非孕妇。然而，泰国女性的这些校正因子在整个孕期相对稳定。种族差异，或饮水量等行为差异可能部分解释了这些差异。这些尿液校正因子的时间变化影响了经稀释调整的尿液邻苯二甲酸代谢物浓度，在韩国和泰国孕妇中均如此。本研究观察表明，在评估孕妇尿液中化学物质的暴露情况时，应考虑尿液校正因子的变化，以避免因妊娠期间发生的生理变化而导致的潜在偏差，并减少暴露分类和关联中的错误。
