Increasing amniotic fluid magnesium concentrations with stable maternal serum levels: A prospective clinical trial

Limor Gortzak-Uzan, Daphna Mezad, Ana Smolin, Michael Friger, Mahmoud Huleihel, Mordechai Hallak

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


OBJECTIVE: To compare the effect of prolonged maternal intravenous MgSO 4 administration on amniotic fluid and serum concentrations of magnesium over time in preterm labor patients. STUDY DESIGN: Patients at 24-34 weeks of singleton gestation who presented with contractions (> 8 in 60 minutes) underwent amniocentesis to rule out intrauterine infection after signing an informed consent form. Some of these women who were clinically judged to have preterm labor received intravenous MgSO 4: a 4-g loading dose followed by a 2 g/h maintenance dose. For technical reasons some patients had amniocentesis performed before initiation of MgSO 4 (controls), while others had the procedure during tocolytic therapy (study subjects). Duration of treatment until amniocentesis was recorded, and blood samples were drawn at the time of amniocentesis. Maternal serum and amniotic fluid magnesium levels were measured using a colorimetric end point method. Data were evaluated using the Student t test and linear regression analysis. RESULTS: Mean magnesium levels in maternal serum rose from 1.74 ± 0.2 mg/dL in controls to 4.01 ± 0.4 mg/dL in the study group. Mean magnesium levels in amniotic fluid were 1.41 ± 0.18 mg/dL in the controls versus 2.28 ± 0.53 mg/dL in in amniotic fluid the treatment group. Duration of MgSO 4 treatment ranged from 3 to 22 hours Amniotic fluid magnesium concentrations increased significantly during therapy (correlation coefficient = 0.89; p < 0.001), while maternal serum levels remained stable over time (correlation coefficient between maternal serum levels and time = -0.39; p = 0.34). CONCLUSION: Although maternal serum magnesium levels remained stable with intravenous MgSO 4 therapy, concentrations continued to rise in amniotic fluid over time. However, amniotic fluid magnesium levels never exceeded maternal serum concentrations during the study period.

Original languageEnglish
Pages (from-to)817-820
Number of pages4
JournalThe Journal of reproductive medicine
Issue number11
StatePublished - 1 Nov 2005


  • Amniotic fluid
  • Magnesium
  • Magnesium sulfate
  • Preterm labor

ASJC Scopus subject areas

  • Reproductive Medicine
  • Obstetrics and Gynecology


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