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Is magnesium sulfate a risk factor for postpartum hemorrhage at the time of cesarean delivery?
Abstract Number: F-37
Abstract Type: Original Research
Uterine atony is the most common cause of postpartum hemorrhage (PPH). Magnesium sulfate is considered to be a risk factor. However, review of the literature reveals a paucity of data in support of this claim. To better understand the role of magnesium on uterine tone, we sought to determine if intrapartum magnesium is a risk factor for PPH at the time of cesarean delivery.
This was a retrospective case control study. The study period was 1/2006 to 8/2011. Selected patients had preeclampsia, received intrapartum magnesium, and underwent cesarean delivery. The next sequential cesarean delivery after each case was selected as a control. Demographic and obstetric data were collected (Table 1). PPH was defined as a ≥ 10 point decrease in hematocrit and/or blood product transfusion. Categorical variables were compared using Pearson chi squared tests. Continuous variables were compared using Kruskal-Wallis equality-of-populations rank tests. Statistical significance was defined as p<0.05. Statistical analysis was performed with STATA Statistics/Data Analysis software (v13.0 StataCorp).
The total number of cesarean deliveries meeting inclusion criteria was 634 (312 cases, 322 controls). More cases than controls had a ≥ 10 point decrease in hematocrit, required transfusion, or required uterotonics, but none of these differences were statistically significant. 22.1% of cases met criteria for PPH, compared to 16.6 % of controls (p=0.07). Logistic regression showed that intrapartum magnesium did not predict a ≥ 10-point decrease in hematocrit (p=0.29). This was also true for PPH (p=0.24). Oxytocin amount was related to PPH among controls, but not cases (p=0.028 vs 0.67). All cases received magnesium prior to delivery, with a mean total dose of 40g. There was no association between magnesium amount and PPH (p=0.13). When controlling for age, fetus number, gestational age at delivery, parity, and BMI, there was no difference in ≥ 10 point decrease in hematocrit (p=0.22) or PPH rates (p=0.18).
We found no association between magnesium use and a decrease in hematocrit by ≥ 10 points or PPH. This relationship held true for the subgroup of patients who labored prior to cesarean delivery. In preeclamptic patients receiving magnesium, we could not confirm a relationship between total amount of oxytocin and PPH.
1. Am J Obstet Gyn 2010;202:353.e1-6
2. Am J Obstet Gyn 2005;193:1056-1060
3. Obstet Gyn 2009;114:669-673