Impact of the change of the atalah standard cut-off point to classify underweight nutritional status during pregnancy

Abstract

Chile, and several Latin American countries, use the Atalah standard to assess nutritional status during pregnancy. However, this standard (underweight: pre-pregnancy body mass index (BMI)<20 kg/m2 and normal weight: pre-pregnancy BMI= 20-24.9 kg/m2) differ from those recommended by the US Institute of Medicine (IOM2009) (underweight: BMI<18.5 kg/m2 and normal weight: 18.5-24.9 kg/m2). Using a large population database from a Chilean public hospital, we compared the prevalence of underweight and normal weight at the beginning of pregnancy with Atalah and IOM2009 standards. Addi-tionally, we evaluated the performance of both standards in detecting adverse neonatal outcomes and gestational weight gain. Methods: Data from clinical records of single birth pregnancies (n= 59,476) at the Sótero del Río Hospital, between 2003-2012 were collected. We compared 1. nutritional status, 2. proportion of excessive gestational weight gain, 3. association between nutritional status and neonatal outcomes (large/small for gestational age, low birth weight, preterm birth and macrosomia), using logistic regression models, and 4. Sensitivity, specificity, and predictive values to predict adverse neonatal outcomes per nutritional status. Results: Pre-pregnancy underweight decreased from 8.6% to 2.5% and women with BMI between 18.5-19.9kg/m2, who exceeded the recommended gestational weight gain increased from 32.7% to 49.2% when using IOM2009 instead of Atalah. Both standards showed low sensitivity, but the IOM2009 cut-off points showed better specificity for identifying healthy newborns. Conclusion: The cut-off points recommended by the IOM2009 better identify the prevalence of underweight and normal weight during pregnancy without increasing neonatal risk. This study supports the recent change of the Ministry of Health in adopting the WHO cut-off points during pregnancy.