Total and ionized serum magnesium and calcium levels during magnesium sulfate administration for preterm labor

OBJECTIVE: This study aimed to estimate the association between total and ionized magnesium, and the changes in serum magnesium and calcium levels in patients with preterm labor during magnesium sulfate (MgSO(4)) administration. METHODS: The study population included 64 women who were candidates for intravenous MgSO(4) treatment for preterm labor. Serial blood samples were taken and measured total magnesium (T-Mg), ionized magnesium (I-Mg), total calcium (T-Ca), and ionized calcium (I-Ca) levels every one-week interval (1st, 2nd, 3rd). RESULTS: There was no significant difference in T-Mg and I-Mg levels during MgSO(4) administration (P>0.05). There was no significant difference in T-Ca and I-Ca levels during MgSO(4) administration (P>0.05). Compared before and after administration of MgSO(4), T-Mg and I-Mg levels and T-Ca levels were changed allow statistically significant (P<0.05). But, there was no significant difference in the I-Ca serum levels before and after MgSO(4) administration (P=0.495). The I-Mg levels for patients with adverse effect were higher than other group but did not reach statistical significance (P>0.05). There was significant correlation between levels of I-Mg and T-Mg (I-Mg=0.395×T-Mg+0.144, P<0.01). CONCLUSION: There were no significant differences in serum Mg and Ca levels during MgSO(4) administration for preterm labor. Compared to the before and after administration of MgSO(4), only I-Ca levels were not substantially changed. There are significant correlations between I-Mg and T-Mg levels during administration of MgSO(4) and I-Mg level seemed to have more correlation with adverse effect than T-Mg.