Maternal-fetal effects of magnesium sulfate on serum osmolality in pre-eclampsia.
OBJECTIVE
To determine the effects of magnesium sulfate therapy on maternal and fetal osmolality in pre-eclampsia.


METHODS
A total of 34 pre-eclamptic women and 22 normal pregnant women participated in the study. Venous blood was drawn upon admission to the labor and delivery unit. Pre-eclamptic patients received standard magnesium sulfate therapy and had a second sample of venous blood drawn 4 h following the beginning of therapy. Fetal umbilical vein blood was obtained immediately following delivery in both groups. Osmolality was measured using a vapor pressure osmometer. Electrolyte levels were measured with a NOVA 8 biomedical analyzer. Data were analyzed via Student's t test, linear regression and correlation with significance established at p < 0.05.


RESULTS
We found no significant difference between the maternal osmolalities of the control and pre-eclamptic groups. Interestingly, fetal cord blood osmolality was significantly lower than maternal osmolality in the normal pregnant women. Sodium levels were also lower, while potassium and ionized calcium levels were higher in the fetal blood. In women with pre-eclampsia treated with magnesium sulfate, there was no difference between the osmolality of the maternal and fetal blood, while potassium and ionized calcium levels were still higher in the fetal blood. Finally, we found no correlation between maternal osmolality and blood pressure.


CONCLUSIONS
High blood pressure in pre-eclampsia is not associated with altered osmolality. An absence of the normal decrease in fetal osmolality is observed in pre-eclamptic women treated with magnesium sulfate.
van der Heyden
J J C
JJ
Department of Obstetrics and Gynecology, Catholic University Nijmegen, The Netherlands.
Standley
C A
CA
D000293:Adolescent; D000328:Adult; D005260:Female; D005312:Fetal Blood / Q000187:drug effects*; D005333:Fetus / Q000502:physiology / Q000503:physiopathology; D006801:Humans; D007262:Infusions, Intravenous; D008278:Magnesium Sulfate / Q000493:pharmacokinetics* / Q000627:therapeutic use; D008431:Maternal-Fetal Exchange / Q000187:drug effects*; D009994:Osmolar Concentration; D011225:Pre-Eclampsia / Q000188:drug therapy*; D011247:Pregnancy / Q000502:physiology*; D015149:Tocolytic Agents / Q000493:pharmacokinetics* / Q000627:therapeutic use
D015149:Tocolytic Agents; D008278:Magnesium Sulfate