61 Maternal mid-upper arm circumference is associated with small for gestational age in a Zambian cohort

Abstract

Low pre-pregnancy body mass index (BMI) increases the risk of small for gestational age (SGA) infants. Alternative anthropometric measures such as mid-upper arm circumference (MUAC) that are easier to obtain than height and weight are needed where resources are scarce. We aimed to quantify the relationship between MUAC and SGA in a pregnant cohort with high HIV prevalence in Zambia. The Zambian Preterm Birth Prevention Study cohort enrolls pregnant women at early antenatal visits in Lusaka, Zambia. Participants are provided standard antenatal care including assessments of demographics, medical history, physical exam including BMI and MUAC, and routine ultrasound. Newborn weight is documented within 24 hours of birth. For this analysis, eligible participants were women with non-anomalous singleton pregnancies. We constructed linear and Poisson regression models adjusting for key confounders to assess the relationship between maternal MUAC and infant birthweight centile (BWC) or SGA, respectively. BWC was calculated using INTERGROWTH-21st references and the primary outcome was defined as severe (<3%ile; SGA3) and moderate SGA (<10%ile; SGA10). We examined the effect of maternal HIV (HIV+ vs HIV-) in all models. The performance of MUAC compared to BMI in predicting SGA was evaluated using ROC analysis. A total of 775 (75%) HIV- and 259 (25%) HIV+ women were included in the analysis. HIV+ women had a lower median baseline MUAC compared to HIV- women (27cm vs 28cm, p=0.01). Increasing maternal MUAC was associated with higher BWC (coeff: 0.95%; p<0.001). The predictive value of MUAC versus BMI for SGA was similar (SGA3: AUC 0.67 vs 0.65; p=0.22 and SGA10: AUC 0.60 vs 0.61; p=0.52). While HIV+ participants did not have an increased risk of SGA3 (RR 0.96, p=0.9) or SGA10 (RR 1.09, p=0.6), maternal HIV increased the effect of MUAC on BWC (coeff: HIV+ 1.48% vs HIV- 0.81%, p=0.004). Early pregnancy mid-upper arm circumference appears to be an alternative to BMI in SGA prediction in Zambia. HIV infection may exacerbate the effect of maternal malnutrition on fetal growth.