Course of Maternal Serum Magnesium Levels in Low-Risk Gestations and in Preterm Labor and Delivery

Abstract

Objectives: To describe the course of total and ionized magnesium and total calcium levels in maternal serum during low-risk pregnancies and to compare women who developed preterm labor and delivery with those who delivered at term. Methods: 209 women with low-risk pregnancies were enrolled in a prospective trial before the 18th week of gestation. No woman received oral magnesium supplementation. The ionized and total magnesium and total calcium levels in maternal serum were measured every 4–6 weeks. The data were grouped into 3 gestational periods (≤18, 19–27 and ≥28 weeks of gestation) for overall comparison and analyzed with the general linear model for repeated measurements and ANOVA. p values of < 0.05 were considered statistically significant. Results: 145 gestations were available for analysis. 27 women were hospitalized for preterm labor and in 16 of these preterm delivery occurred. Ionized and total magnesium and calcium levels were significantly lower after the 18th week of gestation than before. The cation levels in women with preterm labor and delivery did not differ from those with term delivery. Conclusion: Ionized and total magnesium and calcium levels decrease with increasing gestational age. Preterm labor and delivery do not seem to be related to changes in serum cation levels.