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Red Cell Folate — Pregnancy Reference Values

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Red Cell Folate (Whole Blood)

Red cell folate reflects long-term folate status and is superior to serum folate for assessing chronic folate deficiency during pregnancy.

Units Nonpregnant Adult 1st Trimester 2nd Trimester 3rd Trimester
ng/mL 150 – 450 137 – 589 94 – 828 109 – 663
nmol/L 340 – 1020 310 – 1335 213 – 1876 247 – 1502
Physiology in pregnancy
  • Maternal folate requirements increase substantially due to rapid cellular proliferation.
  • Placental transport of folate increases throughout gestation.
  • Red cell folate remains a stable marker of tissue folate stores.
  • Subclinical deficiency may occur despite normal serum folate.
Causes of low red cell folate
  • Poor dietary intake (most common worldwide)
  • Malabsorption (celiac disease, Crohn’s disease, bariatric surgery)
  • Increased requirements (multiple gestation)
  • Chronic hemolysis or rapid erythropoiesis
  • Antifolate medications (methotrexate, phenytoin, trimethoprim, sulfasalazine)
  • Alcohol use disorder
  • Genetic folate cycle disorders (MTHFR, DHFR)
  • Megaloblastic anemia
Causes of elevated red cell folate
  • High-dose folate supplementation
  • Fortified diet with supraphysiologic intake
  • Vitamin B12 deficiency (functional folate trapping)
  • Recent transfusion
  • Reduced erythropoiesis
Special obstetric considerations
  • Low folate is associated with neural tube defects and fetal growth restriction.
  • WHO recommends maintaining RBC folate ≥ 906 nmol/L for optimal NTD prevention.
  • High folate does not cause toxicity but may mask vitamin B12 deficiency.
  • RBC folate is preferred over serum folate in pregnancy assessment.

References

  1. Abbassi-Ghanavati M, Greer LG, Cunningham FG. Pregnancy and laboratory studies. Obstet Gynecol. 2009.
  2. World Health Organization. Optimal RBC folate concentrations in women of reproductive age. 2015.
  3. NIH Office of Dietary Supplements. Folate Fact Sheet for Health Professionals.
  4. O’Leary F, Samman S. Vitamin B12 and folate in pregnancy. Nutrition Reviews. 2010.
  5. Milman N. Folate physiology in pregnancy. Acta Obstet Gynecol Scand. 2006.