Table_1_Maternal cobalt concentration and risk of spontaneous preterm birth: the role of fasting blood glucose and lipid profiles.docx

IntroductionSpontaneous preterm birth (SPB) is a significant cause of neonatal mortality, yet its etiology remains unclear. Cobalt, an essential trace element, might be a risk factor for SPB. This study aims to investigate the relationship between maternal serum cobalt concentration and SPB, and to clarify the role of blood lipids and fasting blood glucose (FBG) in this relationship.
MethodsWe conducted a nested case-control study within the Beijing Birth Cohort Study. Serum samples were obtained from 222 pregnant women with SPB and 224 controls during the first (7–13 weeks of pregnancy) and third trimesters (32–42 weeks of pregnancy). Serum cobalt concentration was determined using inductively coupled plasma mass spectrometry (ICP-MS). Fasting blood glucose and lipids levels were detected using a fully automated biochemical immunoassay instrument. Logistic regression models and linear regression models were established to explore the association between serum cobalt concentration and the risk of SPB in pregnant women, and to test the mediating effect of fasting blood glucose (FBG) and lipids.
ResultsWe found that the serum cobalt concentration in mothers with SPB and controls was similar in the first trimester, with values of 0.79 (0.58–1.10) ng/mL and 0.75 (0.51–1.07) ng/mL, respectively. However, in the third trimester, the cobalt concentration increased to 0.88 (0.59–1.14) ng/mL and 0.84 (0.52–1.19) ng/mL, respectively. In the logistic regression model, when considering the third trimester of pregnancy, after adjusting for ethnicity, pre-pregnancy body mass index (BMI), maternal age, education, income, and parity, it was observed that the medium level of cobalt concentration (0.63–1.07 ng/ml) had a negative correlation with the risk of SPB. The odds ratio (OR) was 0.56, with a 95% confidence interval of 0.34–0.90 ng/mL and a p-value of 0.02. This suggests that cobalt in this concentration range played a protective role against SPB. Additionally, it was found that FBG in the third trimester of pregnancy had a partial intermediary role, accounting for 9.12% of the association. However, no relationship between cobalt and SPB risk was found in the first trimester.
ConclusionDuring the third trimester, intermediate levels of maternal cobalt appear to offer protection against SPB, with FBG playing a partial mediating role. To further clarify the optimal cobalt concentrations during pregnancy for different populations, a multi-center study with a larger sample size is necessary. Additionally, exploring the specific mechanism of FBG’s mediating role could provide valuable insights for improving the prevention of SPB.

引言
自发性早产（SPB）是新生儿死亡的重要诱因之一，但其病因学机制至今尚未明确。钴作为一种必需微量元素，可能是SPB的潜在危险因素。本研究旨在探讨孕妇血清钴浓度与SPB之间的关联，并阐明血脂与空腹血糖（FBG）在该关联中所起的作用。

方法
本研究依托北京出生队列研究开展巢式病例对照研究。研究采集了222例SPB孕妇与224例对照孕妇在妊娠早期（孕7~13周）及妊娠晚期（孕32~42周）的血清样本。采用电感耦合等离子体质谱法（ICP-MS）检测血清钴浓度；通过全自动生化免疫分析仪检测空腹血糖与血脂水平。构建Logistic回归模型与线性回归模型，以探讨孕妇血清钴浓度与SPB发病风险之间的关联，并验证空腹血糖（FBG）与血脂的中介效应。

结果
本研究发现，妊娠早期SPB组与对照组孕妇的血清钴浓度水平相近，分别为0.79（0.58~1.10）ng/mL与0.75（0.51~1.07）ng/mL。但在妊娠晚期，两组血清钴浓度分别升至0.88（0.59~1.14）ng/mL与0.84（0.52~1.19）ng/mL。在针对妊娠晚期的Logistic回归分析中，经种族、孕前体质量指数（BMI）、孕妇年龄、受教育程度、收入水平及产次校正后，观察到中等浓度范围（0.63~1.07 ng/mL）的钴与SPB发病风险呈负相关，其优势比（OR）为0.56，95%置信区间为0.34~0.90，P值为0.02。这表明该浓度范围内的钴对SPB具有保护作用。此外，研究发现妊娠晚期空腹血糖（FBG）发挥了部分中介作用，占总关联效应的9.12%。但在妊娠早期，未观察到钴浓度与SPB发病风险存在显著关联。

结论
妊娠晚期孕妇体内中等浓度的钴可对SPB起到保护作用，空腹血糖（FBG）在此过程中发挥部分中介效应。为进一步明确不同妊娠人群的最优血清钴浓度范围，尚需开展更大样本量的多中心研究。此外，阐明空腹血糖中介效应的具体作用机制，可为SPB的预防干预提供新的研究思路与理论依据。