Vitamin D plays a vital role in successful pregnancy outcomes for both the mother and fetus. Vitamin D is bound to vitamin D binding protein (VDBP) in blood and is carried to the liver, kidneys and other target tissues. Accurate measurements of the clinically measured metabolite of vitamin D, 25-hydroxyvitamin D [25(OH)D], depend on complete removal from the binding protein. It has been found that VDBP concentrations increase in maternal serum during pregnancy, obfuscating the accuracy of 25(OH)D concentration measurements in pregnant women. Additionally, measurements of VDBP concentrations during pregnancy have been performed using immunoassays, which suffer from variations due to differences in antibody epitopes, making clinical comparisons difficult. Quantification of VDBP is also of interest because changes in VDBP expression levels may indicate negative outcomes during pregnancy, such as preterm delivery and restricted fetal growth. To address the need for accurate measurement of VDBP during pregnancy, a method using liquid chromatography-isotope dilution mass spectrometry (LC-IDMS) was developed to quantify VDBP using isotopically labeled peptides as internal standards. This method was used to quantify VDBP in Standard Reference Material® (SRM) 1949 Frozen Human Prenatal Serum, which was prepared from separate serum pools of women who were not pregnant and women during each trimester of pregnancy. VDBP concentrations were found to be lowest in the serum pool from non-pregnant women and increased in each trimester. These data had good repeatability and were found to be suitable for reference value assignment of VDBP in SRM 1949.

维生素 D 在母亲和胎儿的成功妊娠结局中起着至关重要的作用。维生素 D 与血液中的维生素 D 结合蛋白 (VDBP) 结合，并被运送到肝脏、肾脏和其他靶组织。临床测量的维生素 D 代谢物 25-羟基维生素 D [25(OH)D] 的准确测量取决于从结合蛋白中完全去除。已经发现怀孕期间母体血清中的 VDBP 浓度会增加，从而混淆了孕妇 25(OH)D 浓度测量的准确性。此外，怀孕期间 VDBP 浓度的测量是使用免疫测定法进行的，由于抗体表位的差异，免疫测定法会发生变化，这使得临床比较变得困难。VDBP 的量化也很有趣，因为 VDBP 表达水平的变化可能表明怀孕期间的负面结果，例如早产和胎儿生长受限。为了满足在怀孕期间准确测量 VDBP 的需求，开发了一种使用液相色谱 - 同位素稀释质谱 (LC-IDMS) 的方法，以使用同位素标记的肽作为内标对 VDBP 进行量化。该方法用于量化标准参考物质® (SRM) 1949 冷冻人产前血清中的 VDBP，该血清是从未怀孕的妇女和怀孕每个三个月期间的妇女的不同血清库中制备的。发现 VDBP 浓度在来自非孕妇的血清库中最低，并在每个孕期增加。