ArticleBMC pregnancy and childbirth2026
Reference intervals for blood concentrations of folate-related biomarkers in early pregnancy among pregnant women in Qingdao.
Article in BMC pregnancy and childbirth, 2026. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Not yet cited in PubMed.
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Abstract
backgroundTo establish reference intervals (RIs) for red blood cell (RBC) folate, vitamin B12, homocysteine, and 5-methyltetrahydrofolate (5-MTHF) during the first trimester of pregnancy among women in the Qingdao region, stratified by age, body mass index (BMI), and total folate intake categories.
methodsA cross-sectional study was conducted involving 2,911 pregnant women (9 to 13
resultsThe biomarker concentrations are reported as median (interquartile range): Vitamin B12: 525.00 (422.50,663.50) pg/mL; RBC folate: 421.41 (327.14,558.14) ng/mL; homocysteine:6.3 (5.5,7.2) µmol/L, and 5-MTHF: 27.78 (19.28,39.24) ng/mL. Significant age-related and BMI-associated differences in biomarker levels were identified (P < 0.05). Age and BMI related differences in biomarker concentrations were mainly reflected in median values. Women aged ≥ 35 years had higher median levels of vitamin B12 (536.00 vs. 520.00 pg/mL), RBC folate (444.19 vs. 411.16 ng/mL), and 5-MTHF (28.38 vs.27.46 ng/mL), but lower median homocysteine (6.2 vs. 6.3 µmol/L) compared with women < 35 years (P < 0.05). Across BMI categories (underweight, normal weight, overweight, obese), median vitamin B12 varied (584.88, 578.54, 537.52, 532.26 pg/mL, P < 0.001), while RBC folate showed a progressively increasing trend (441.03, 457.18, 477.69, 483.66 ng/mL, P = 0.003). Median homocysteine (6.4, 6.2, 6.3, 6.4 µmol/L) and 5-MTHF (30.61, 30.80, 29.67, 27.42 ng/mL) also differed significantly across BMI groups (P < 0.001). Furthermore, biomarker concentrations demonstrated clear trends across quartiles of total folate intake: RBC folate, vitamin B12, and 5-MTHF increased progressively from Q1 to Q4, while homocysteine decreased (all P < 0.001).
conclusionThis study characterized the distribution of RBC folate, vitamin B12, homocysteine, and 5-MTHF concentrations in early pregnancy (9-13
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