Risk stratification for small for gestational age for the Brazilian population: a secondary analysis of the Birth in Brazil study

Abstract

Risk-stratification screening for SGA has been proposed in high-income countries to prevent perinatal morbidity and mortality. There is paucity of data from middle-income settings. The aim of this study is to explore risk factors for SGA in Brazil and assess potential for risk stratification. This population-based study is a secondary analysis of Birth in Brazil study, conducted in 266 maternity units between 2011 and 2012. Univariate and multivariate logistic regressions were performed, and population attributable fraction estimated for early and all pregnancy factors. We calculated absolute risk, odds ratio, and population prevalence of single or combined factors stratified by parity. Factors associated with SGA were maternal lupus (ORadj 4.36, 95% CI [2.32–8.18]), hypertensive disorders in pregnancy (ORadj 2.72, 95% CI [2.28–3.24]), weight gain < 5 kg (ORadj 2.37, 95% CI [1.99–2.83]), smoking at late pregnancy (ORadj 2.04, 95% CI [1.60–2.59]), previous low birthweight (ORadj 2.22, 95% CI [1.79–2.75]), nulliparity (ORadj 1.81, 95% CI [1.60–2.05]), underweight (ORadj 1.61, 95% CI [1.36–1.92]) and socioeconomic status (SES) < 5th centile (ORadj 1.23, 95% CI [1.05–1.45]). Having two or more risk factors (prevalence of 4.4% and 8.0%) was associated with a 2 and fourfold increase in the risk for SGA in nulliparous and multiparous, respectively. Early and all pregnancy risk factors allow development of risk-stratification for SGA. Implementation of risk stratification coupled with specific strategies for reduction of risk and increased surveillance has the potential to contribute to the reduction of stillbirth in Brazil through increased detection of SGA, appropriate management and timely delivery.