Effect of MgSO4 on heart rate monitoring in the preterm fetus.
OBJECTIVE
To evaluate in a controlled, blind fashion, using both subjective and objective criteria, whether MgSO4 is associated with clinically significant changes in fetal heart rate monitoring.


METHODS
Fetal heart rate tracings were prospectively collected before and after MgSO4 loading in 50 preterm labor patients. Three obstetricians, blind to treatment status, graded the tracings using both subjective and objective criteria.


RESULTS
The baseline fetal heart rate declined slightly after therapy. Subjective, but not objective, evaluation demonstrated a greater likelihood of decreased variability after MgSO4 loading. There was no difference in periodic changes after MgSO4 loading. Multiple regression analysis showed a greater likelihood of decreased variability at earlier gestational ages but no relationship to the serum magnesium level.


CONCLUSIONS
Magnesium sulfate tocolysis is associated with a subjective decrease in fetal heart rate variability in the preterm fetus.
Wright
J W
JW
Coastal Area Health Education Center, Wilmington, NC 28402-9025, USA.
Ridgway
L E
LE
Wright
B D
BD
Covington
D L
DL
Bobitt
J R
JR
D016903:Drug Monitoring; D005260:Female; D005323:Fetal Monitoring; D005865:Gestational Age; D006340:Heart Rate, Fetal / Q000187:drug effects*; D006801:Humans; D008278:Magnesium Sulfate / Q000627:therapeutic use*; D007752:Obstetric Labor, Premature / Q000188:drug therapy*; D011247:Pregnancy; D011446:Prospective Studies; D012044:Regression Analysis; D016037:Single-Blind Method; D015149:Tocolytic Agents / Q000627:therapeutic use*
D015149:Tocolytic Agents; D008278:Magnesium Sulfate