Reproductive Endocrinology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, No 24, Parvane Street, Yaman Street, Velenjak, Tehran, Iran.
Department of Social Medicine, Faculty of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.
Arch Gynecol Obstet. 2022 Feb;305(2):495-504. doi: 10.1007/s00404-021-06163-y. Epub 2021 Jul 31.
To evaluate the total, and direct effects of vitamin D, measured by circulating 25-hydroxyvitamin D [25(OH)D] levels, on GWG after adjustment for confounding variables, and then assess the indirect effects by demonstrating the role of gestational age at birth as a mediator in this association.
Data collected in "Khuzestan Vitamin D Deficiency Screening Program in Pregnancy" were used for the present study; it included the data of 900 pregnant women referred to the health centers of Shushtar (Khuzestan Province, Iran), whose vitamin D status during the third trimester of pregnancy was available. A mediation analysis was applied to detect the causal relationship between serum level of 25(OH)D, covariates (maternal age, parity, education level, and baseline maternal weight), mediator (gestational age), and outcome (GWG).
Of 900 pregnant women referred to the health centers, a total of 726 eligible participants were analyzed for the study. The adjusted total effect of vitamin D on GWG was estimated 0.07 (95% CI 0.06, 0.09; P = 0.000). This study also revealed adjusted direct effect of vitamin D on GWG was statistically significant 0.02 (95% CI: 0.003, 0.04; P = 0.021). In addition, the adjusted indirect effect of this micronutrient on GWG by considering gestational age as a mediator was found to be significant [0.05 (95% CI 0.04, 0.06; P = 0.000)]. This study revealed an increase in the trend of weight gain during pregnancy trimesters for women with different levels of 25(OH)D; however, women with severe vitamin D deficiency had the lowest speed as compared to moderate and normal levels.
This study shows that maternal vitamin D status directly affects the gestational weight gain independent of gestational age. Therefore, the detection and treatment of women with vitamin D inadequacy can directly improve the trend of their weight gain in addition to its indirect effect on reducing the risk of preterm delivery.
评估通过循环 25-羟维生素 D [25(OH)D] 水平测量的维生素 D 对 GWG 的总效应和直接效应，然后通过证明出生时的胎龄在该关联中的中介作用来评估间接效应。
本研究使用了“库泽斯坦妊娠维生素 D 缺乏筛查计划”中收集的数据；它包括 900 名被转诊到舒什塔尔（伊朗胡齐斯坦省）卫生中心的孕妇的数据，这些孕妇在妊娠晚期的维生素 D 状况可用。应用中介分析来检测血清 25(OH)D、协变量（母亲年龄、产次、教育水平和基线母亲体重）、中介（胎龄）和结局（GWG）之间的因果关系。
在被转诊到卫生中心的 900 名孕妇中，共有 726 名符合条件的参与者被纳入研究。维生素 D 对 GWG 的调整后总效应估计为 0.07（95%CI 0.06，0.09；P=0.000）。本研究还表明，维生素 D 对 GWG 的调整后直接效应具有统计学意义，为 0.02（95%CI：0.003，0.04；P=0.021）。此外，通过将胎龄视为中介，发现这种微量营养素对 GWG 的调整后间接效应具有显著性[0.05（95%CI 0.04，0.06；P=0.000)]。本研究表明，不同 25(OH)D 水平的孕妇在妊娠期间体重增加的趋势增加；然而，与中度和正常水平相比，维生素 D 严重缺乏的孕妇体重增加速度最慢。
本研究表明，母体维生素 D 状态直接影响独立于胎龄的妊娠期体重增加。因此，检测和治疗维生素 D 不足的女性可以直接改善她们的体重增加趋势，除了间接降低早产风险外。
