Urinary concentrations of gamma-hydroxybutyric acid and related compounds in pregnancy

J Anal Toxicol. 2010 Sep;34(7):394-9. doi: 10.1093/jat/34.7.394.


Endogenous production complicates the interpretation when gamma-hydroxybutyric acid (GHB) is measured in urine for forensic purposes. We performed a cross-sectional study to test the hypothesis that pregnant women have higher levels of urinary GHB than non-pregnant controls, and thus increased risk of false-positive GHB tests. GHB, gamma-butyrolactone (GBL) and beta-hydroxybutyric acid (BHB) concentrations in urine from 66 pregnant women and 69 non-pregnant controls were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS-MS). The mean GHB, GBL, and BHB concentrations were 0.36, 0.34 and 1.92 mg/L in the pregnant women, and 0.24, 0.08 and 0.40 mg/L in the control group. The pregnant women had significantly higher levels of GHB (1.5-fold), GBL (4.3-fold), and BHB (4.8-fold). Creatinine-adjusted GHB concentrations were similar in both groups. Pregnant women have higher urinary levels of GHB, GBL, and BHB. In LC-MS-MS assays not distinguishing between GHB and BHB, there is a significantly increased risk of false-positive GHB tests in pregnant women. This false-positive rate can be reduced by correcting for creatinine concentration, by using GHB-specific assays or by introducing higher interpretative cut-off levels for pregnant women in assays that do not discriminate between GHB and GBL or BHB.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3-Hydroxybutyric Acid / urine*
  • 4-Butyrolactone / urine*
  • Chromatography, Liquid
  • Cross-Sectional Studies
  • False Positive Reactions
  • Female
  • Forensic Toxicology
  • Humans
  • Hydroxybutyrates / urine*
  • Pregnancy / urine*
  • Reference Values
  • Reproducibility of Results
  • Tandem Mass Spectrometry


  • Hydroxybutyrates
  • 4-hydroxybutyric acid
  • 4-Butyrolactone
  • 3-Hydroxybutyric Acid