Vitamin A, Retinol (serum)
Serum retinol concentration declines slightly during pregnancy due to hemodilution and increased maternal–fetal transfer. Severe deficiency or excess can both have fetal risks, making interpretation clinically important.
| Units | Nonpregnant Adult | 1st Trimester | 2nd Trimester | 3rd Trimester |
|---|---|---|---|---|
| µg/dL | 20 – 100 | 25 – 55 | 31 – 49 | 23 – 49 |
| µmol/L | 0.7 – 3.5 | 0.87 – 1.91 | 1.07 – 1.71 | 0.79 – 1.71 |
Pregnancy physiology
- Retinol-binding protein decreases in pregnancy, lowering total retinol concentration.
- Hemodilution contributes to reduced measured serum levels.
- Fetal demand for vitamin A increases as organogenesis progresses.
- Despite lower serum levels, clinical deficiency is rare in well-nourished populations.
Causes of low retinol
- Malnutrition or fat malabsorption
- Chronic liver disease
- Protein deficiency (low retinol-binding protein)
- Severe infection or inflammation (acute phase response)
- Normal physiologic reduction during pregnancy
Causes of elevated retinol
- Excess vitamin A supplementation
- Liver hypervitaminosis A
- Isotretinoin use (teratogenic risk)
Clinical caution: Excess vitamin A in pregnancy is associated with fetal anomalies, particularly when intake exceeds 10,000 IU/day of preformed retinol.
References
- Lockitch G. Handbook of Diagnostic Biochemistry and Hematology in Normal Pregnancy. CRC Press; 1993.
- Abbassi-Ghanavati M, Greer LG, Cunningham FG. Pregnancy and laboratory studies: a reference table for clinicians. Obstet Gynecol. 2009;114:1326–31.