Reproductive
Vitamin D, Free vitamin D, Iron, Ferritin, and Hemoglobin in Pregnancy: Findings from Kuwait Birth Cohort Study Abdullah Al-Taiar* Abdullah Al-Taiar Ali H. Ziyab Reem Al-Sabah Majeda S. Hammoud
Background: The association between vitamin D and iron, ferritin, or hemoglobin (Hb) levels remains controversial. This study aimed to estimate the prevalence of vitamin D deficiency and investigate its association with iron, ferritin, and Hb levels in pregnant women.
Methods: Pregnant women in their second or third trimester were recruited in the Kuwait birth cohort, a prospective study. 25-hydroxyvitamin D (25OHD) was assessed using electrochemiluminescence immunoassay, with deficiency defined as <50 nmol/L; while anemia was defined as having Hb <110 g/L. Free 25OHD was calculated from the concentrations of total 25OHD, vitamin D binding protein (VDBP) and albumin. Data on socio-economic status and lifestyle were collected using personal interviews. Simultaneous-quantile regression was used to examine the association between 25OHD levels and each iron, ferritin, and Hb levels while adjusting for potential confounders. Logistic regression was used to investigate the association between vitamin D deficiency and each iron, ferritin, and Hb levels while adjusting for potential confounders.
Results: Of all study participants, 55.93% (95%CI: 52.94-58.88%) had vitamin D deficiency, and 21.54% (95%CI: 19.21- 24.06%) had severe deficiency. Weak but significant correlations were found between 25OHD levels and iron (Spearman’s correlation coefficient (rs)=0.15; p<0.001), ferritin (rs=0.17; p<0.001), and Hb levels (r=0.14; p<0.001). There was also a strong association between vitamin D deficiency and anemia (p= 0.003). These associations remained evident after adjusting for confounding factors. Similar results were obtained when Free 25OHD was used instead of total 25OHD.
Conclusion: Vitamin D deficiency is common among pregnant women in Kuwait. There is a significant association between 25OHD and each iron, ferritin and Hb, which highlights the importance of routine screening for both anemia and vitamin D deficiency to guide appropriate prenatal supplementation.