Background: The aim of this study was to describe the contribution of prematurity and small for gestational age (SGA) to low birth weight (LBW) as well as to identify risk factors associated with preterm birth and SGA and to explore their impact on birth weight.
Methods: A cross-sectional study was carried out in southern Benin between June 2007 and July 2008. At delivery, women's characteristics and newborn's anthropometric measurements were collected. Gestational age was estimated using the Ballard method; SGA was defined using the William's reference curve. Analyses were performed by multiple logistic and linear regressions.
Results: In total, 526 mother-infant pairs were enrolled. LBW (<2500 g), prematurity (<37 weeks) and SGA accounted for 9.1%, 10.3% and 25.3% of the sample, respectively. Infant's male gender was associated with a lower risk of prematurity (p=0.03). Low maternal anthropometric status (p<0.001), primiparity (p=0.017) and infant's male gender (p=0.015) were associated with an increased risk of SGA. Only low maternal anthropometric status and primiparity were associated with an increased risk of LBW, and their effect on LBW was mediated by SGA.
Conclusions: SGA was the main mechanism mediating the effect of risk factors on LBW. Maternal undernutrition (either short stature or low anthropometric status) was the most important of them.
Keywords: Intrauterine growth restriction; Low birth weight; Maternal undernutrition; Prematurity; Risk factors; Small for gestational age.