Evaluating Mid-Upper Arm Circumference Cut-Offs as a Screening Tool for Undernutrition in Pregnant Women: An Alternative to Body Mass Index

BackgroundUndernutrition during pregnancy is a major public health issue and may lead to negative pregnancy outcomes. The body mass index (BMI), considered widely used as the reference method for assessing nutritional status due to its established population-based cut-off points; however, it can be misleading in pregnancy. This study aimed to validate the mid-upper arm circumference (MUAC) as a screening tool for identifying undernourished pregnant women (PW) in an urban slum, compared to BMI. MethodsData for this analysis were extracted from studies conducted in Bauniabadh, a slum located in Dhaka, Bangladesh. The final sample size was 375 PW aged 15-39 years with a gestational age of <14 weeks. The first recorded weight during enrolment was considered a proxy for pre-pregnancy weight. Participants were classified as undernourished or well-nourished accordingly. The BMI Z-scores for adolescents and the BMI categories for adult women were used to define undernutrition. Receiver operating characteristic (ROC) curve analysis was used to calculate the area under the curve (AUC), sensitivity, specificity, predictive values, and likelihood ratios. BMI-MUAC concordance was analyzed using McNemars test to determine optimal MUAC cut-offs. ResultsAmong the candidate MUAC cut-off values, a threshold of <22.5 cm demonstrated high diagnostic accuracy, with 78.1% sensitivity, 92.9% specificity, an AUC of 85.5%, and a positive likelihood ratio (LR+) of 11.0. The alternative threshold of <23.0 cm showed higher sensitivity (84.4%) and AUC (86.9%) but lower specificity (89.4%) and LR+ (7.9). The difference in AUCs between the two thresholds was not statistically significant (p = 0.400). Using the <22.5 cm cut-off, 19.2% of pregnant women were classified as undernourished compared with 17.1% based on BMI. Concordance between MUAC <22.5 cm and BMI-defined undernutrition was satisfactory (p=0.182). ConclusionsMUAC can be considered a simple and effective screening tool for identifying undernutrition in PW. Given its strong diagnostic accuracy, a threshold of <22.5 cm may be a practical alternative to BMI and considered for integration into nutritional programs for PW in Bangladesh.