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Gamma-Glutamyl Transferase (GGT) — Pregnancy Reference Values

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Gamma-Glutamyl Transferase (GGT)

Gamma-glutamyl transferase is a hepatobiliary enzyme involved in glutathione metabolism and membrane transport. In normal pregnancy, serum GGT levels are typically reduced compared with non-pregnant adults.

Units Nonpregnant Adult 1st Trimester 2nd Trimester 3rd Trimester
U/L 9 – 58 2 – 23 4 – 22 3 – 26
µkat/L 0.15 – 0.97 0.03 – 0.38 0.07 – 0.37 0.05 – 0.43
Physiology in pregnancy
  • Serum GGT is typically reduced in pregnancy due to altered hepatic enzyme activity and hemodilution.
  • Placenta contributes minimally to circulating GGT.
  • Unlike alkaline phosphatase, GGT does not show a physiologic late-pregnancy rise.
  • Low values in pregnancy are usually physiologic and not pathologic.
Causes of low GGT
  • Normal physiologic suppression in pregnancy
  • Hypothyroidism
  • Rare inherited GGT deficiency
  • Severe vitamin C deficiency
  • Laboratory assay variation
Causes of elevated GGT
  • Biliary obstruction (cholelithiasis, strictures)
  • Drug-induced liver injury (phenytoin, carbamazepine, valproate, barbiturates)
  • Alcohol use
  • Metabolic-associated fatty liver disease (NAFLD/NASH)
  • Viral hepatitis (HBV, HCV)
  • Autoimmune cholestatic disease (PBC, PSC)
  • Right-sided heart failure with hepatic congestion
  • Pancreatic disease
  • Enzyme induction from chronic medications
Special obstetric considerations
  • GGT is often normal in intrahepatic cholestasis of pregnancy and should not be used alone for diagnosis.
  • Disproportionate elevation of GGT with ALP suggests hepatobiliary rather than placental origin.
  • Marked elevation should prompt evaluation for biliary obstruction, viral hepatitis, or drug toxicity.
  • Isolated mild elevation without symptoms is frequently benign.

References

  1. Abbassi-Ghanavati M, Greer LG, Cunningham FG. Pregnancy and laboratory studies. Obstet Gynecol. 2009.
  2. Pratt DS, Kaplan MM. Evaluation of abnormal liver enzymes. New England Journal of Medicine.
  3. Ovadia C et al. Intrahepatic cholestasis of pregnancy and perinatal outcomes. Lancet. 2019.
  4. Whitfield JB. Gamma-glutamyl transferase. Crit Rev Clin Lab Sci. 2001.
  5. SMFM Consult Series #53. Intrahepatic cholestasis of pregnancy.
  6. LiverTox: Clinical and Research Information on Drug-Induced Liver Injury. NIH.