The aim of our investigation was to study the Serum magnesium levels in preterm labour and to compare these values with those patients who had a term delivery ,to find associated signs and symptoms and to suggest nutritional correction of prognostic value Methods:-A case-control study was carried out to evaluate serum magnesium levels and associated symptoms in women with preterm labour (28-36 weeks) and compare them with patients in same gestational age who delivered at term(37-40 weeks). Results:-Patients in preterm labor have a significantly depressed serum magnesium level [mean, 1.343± 0.09meq/l vs 1.875 ± 0.013meq/l] (p<0.001 ) as compared to normal pregnancy. Preterm labour cases differed from controls in terms of significantly higher incidence of muscle cramps and change in the quality or quantity of vaginal discharge ( p< 0.001). In our study, fall in the value of serum magnesium levels was of a significant magnitude in preterm labour as compared to normal controls(p<0.001).Percentage of patients with preterm labour belonging to low socio-economic class was significantly higher than the upper and middle socio-economic classes (p < 0.05). Conclusion:-Estimation of serum magnesium levels may be a useful parameter in pregnancy. Magnesium supplementation should be considered in pregnancy especially in high risk groups.