Dose-response association between maternal body mass index and small for gestational age: a meta-analysis

Objective: This study was performed to determine the dose-response relationships between maternal anthropometric variables and risk of small for gestational age (SGA).Methods: Linear and nonlinear dose-response meta-analyses were performed to summarize the adjusted relative risks of SGA. Ten databases, including PubMed (MEDLINE), were searched. Study quality was assessed using the Newcastle-Ottawa scale.Results: A total of 323 243 subjects were extracted from high-quality studies to evaluate maternal body mass index (BMI) (n=9). The generalizability of the findings regarding height and weight (n=3 and 2, respectively) was limited. The non-linear model (p for non-linearity <0.05) showed a significant and inverse association of maternal BMI with risk of SGA, although only two of nine studies involved obese women (i.e. BMI30kg/m(2)). The slope of the dose-response curve between maternal BMI and SGA (i.e. the amount of reduction in SGA risk) decreased gradually.Conclusions: SGA risk may be reduced by increasing BMI of normal (i.e. 18.5kg/m(2) BMI<25kg/m(2)) and overweight women (i.e. 25kg/m(2)BMI<30kg/m(2)), but the most marked reduction is achieved by increasing BMI of underweight women (i.e. BMI<18.5kg/m(2)).