Frequency of Hypomagnesemia in Women Undergoing Preterm Labor

Background: Preterm labor is a major contributor to neonatal morbidity and mortality, and micronutrient disturbances such as hypomagnesemia may influence myometrial excitability and early uterine activity. Objective: To determine the frequency of hypomagnesemia among women presenting with spontaneous preterm labor and to assess its distribution across key maternal and clinical characteristics. Methods: A descriptive cross-sectional study was conducted in the Department of Obstetrics and Gynecology, Allied Hospital Faisalabad, over six months. Women aged 18–40 years with singleton gestation, intact membranes, and spontaneous preterm labor (<37 weeks) were enrolled by consecutive sampling after informed consent. Maternal age, parity, gestational age, and BMI were recorded. Venous blood (3 mL) was obtained on admission before magnesium-containing therapy and analyzed in a single laboratory; hypomagnesemia was defined as serum magnesium <1.46 mg/dL. Associations were examined using chi-square testing and logistic regression. Results: Among 185 women, hypomagnesemia occurred in 128 (69.2%; 95% CI: 62.1%–75.5%). Prevalence was highest in underweight (88/91, 96.7%) and obese women (32/37, 86.5%) compared with normal BMI (2/39, 5.1%) (p<0.001) and was more frequent at <28 weeks (84/103, 81.6%) than 32–36+6 weeks (12/41, 29.3%) (p<0.001). Underweight BMI and obesity remained independently associated with hypomagnesemia in multivariable analysis. Conclusion: Hypomagnesemia is highly prevalent in women presenting with preterm labor, particularly among those at BMI extremes and earlier gestations, supporting consideration of targeted antenatal magnesium assessment and further prospective interventional research.