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Alpha-1-antitrypsin (A1AT) — Pregnancy Reference Values

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Alpha-1-antitrypsin (A1AT) — Serum

Alpha-1-antitrypsin (A1AT) is a major acute-phase protein synthesized by the liver. Levels normally rise during pregnancy as part of the physiologic inflammatory response and increase progressively across trimesters.

Units Nonpregnant Adult 1st Trimester 2nd Trimester 3rd Trimester
mg/dL 100 – 200 225 – 323 273 – 391 327 – 487
g/L 1 – 2 2.3 – 3.2 2.7 – 3.9 3.3 – 4.9
Pregnancy physiology
  • A1AT is a positive acute-phase reactant whose synthesis increases during pregnancy.
  • Levels are typically higher than in nonpregnant adults and rise with advancing gestation.
  • Interpretation should incorporate liver tests, inflammatory markers, and clinical symptoms.
Causes of low A1AT
  • Inherited alpha-1-antitrypsin deficiency
    • Severe variants: PiZZ, PiSZ, other deficiency alleles
    • Associated with emphysema and neonatal/pediatric liver disease
  • Reduced hepatic synthesis
    • Advanced cirrhosis or liver failure
    • Severe acute hepatic necrosis
  • Protein loss
    • Nephrotic syndrome
    • Protein-losing enteropathy
    • Extensive burns / exudative wounds
  • Malnutrition and catabolic states
  • Pregnancy-specific considerations
    • Values below the pregnancy-adjusted range may suggest inherited deficiency or hepatic dysfunction.
    • Persistent low A1AT with jaundice or abnormal LFTs warrants phenotyping/genotyping.
Causes of elevated A1AT
  • Physiologic elevation in pregnancy
    • Normal acute-phase response
  • Inflammation
    • Bacterial or viral infections
    • Autoimmune or systemic inflammatory disease
    • Inflammatory bowel disease
  • Liver disease with preserved synthetic function
    • Cholestasis (including ICP)
    • Chronic hepatitis
    • Early cirrhosis
  • Tissue injury and malignancy
    • Major trauma or surgery
    • Burns
    • Certain malignancies
  • Pregnancy-specific notes
    • Moderate elevation may be physiologic.
    • Marked elevation with abnormal liver tests should prompt evaluation for cholestasis, infection, or HELLP.

References

  1. Abbassi-Ghanavati M, Greer LG, Cunningham FG. Pregnancy and laboratory studies: a reference table for clinicians. Obstet Gynecol. 2009;114:1326–31.
  2. Wallach J. Interpretation of Diagnostic Tests, 8th ed.
  3. Fischbach FT, Dunning MB. A Manual of Laboratory and Diagnostic Tests, 7th ed.