Placental DNA extraction
DNA extraction from placental tissue was performed according to an adapted protocol9 from Purelink Genomic DNA commercial kit (Life Technologies, Carlsbad, CA). DNA quality was estimated by PCR of human CCR2 and HLAG genes. PCR products were assessed by electrophoresis on 1.5% agarose gels stained with Blue Green Loading Dye (LGC Biotecnologia®, São Paulo, Brazil) and then visualized by UV light.