To evaluate the comparison between maternal serum magnesium levels in preterm and term labour. Material and methods:One hundred subjects who met certain criteria had a venous blood sample taken. There were two cohorts: Group-1 (preterm labour) consisting of fifty subjects and Group-2 (term labour) consisting of fifty subjects. The level of magnesium in the serum was estimated in the two cohorts. SPSS software was used for evaluation. Results: Women with preterm labour had a significantly reduced serum magnesium level with a mean serum magnesium level of 1.83 mg/dl whereas the patients with term labour had a mean serum magnesium level of 2.42 mg/dl. Conclusions: Serum magnesium level can be used as a predicting tool for preterm labour