(P27-059-25) Holotranscobalamin Concentrations Across Human Pregnancy: A Systematic Review

Objectives: Holotranscobalamin (holoTC) represents the portion of vitamin B12 that is actively transported in the bloodstream and delivered to cells. While holoTC is considered the most sensitive biomarker for assessing vitamin B12 status, there is limited research to examine holoTC in human pregnancy. We aimed to assess whether holoTC concentrations change across pregnancy.

Methods: We conducted a systematic review of original, peer-reviewed longitudinal studies in PubMed, Web of Science, and Centre for Agriculture and Biosciences International (CABI) Abstracts databases from inception through April 2024. Eligible studies reported blood concentrations of holoTC in at least two pregnancy timepoints in humans. Four authors independently conducted article review and data extraction. We performed a narrative synthesis to compile the results and summarized data in tables and figures. We calculated percentage change between timepoints for each study

Results: Twelve studies were eligible for inclusion. Only one study reported concentrations of holoTC from preconception through labor. From the first to the second trimester, holoTC concentrations decreased (5-28%) in 7 studies, increased (2%) in 1 study, and remained unchanged in 1 study. From the second to the third trimester, holoTC concentrations decreased (6-16%) in 3 studies, increased (1-31%) in 4 studies, and did not change in 1 study. Overall, from the first to third trimesters, holoTC concentrations decreased (4-22%) in 4 studies and increased by 7% in 1 study.

Conclusions: In longitudinal pregnancy studies, there was an overall decrease in holoTC concentrations from the first to second trimesters and the first to third trimesters, but there was an inconsistent pattern from second to third trimester.

Funding Sources: A portion of time preparing this manuscript was supported by the Health Resources and Services Administration (HRSA) of the U.S. Department of Health and Human Services (HHS) as part of Maternal Child Health Bureau Nutrition Training Grant, The TRANSCEND Program in Maternal Child Health Nutrition (T7949101; PI: Bruening). The contents are those of the author(s) and do not necessarily represent the official views of, nor an endorsement, by HRSA, HHS or the U.S. Government.