Total mRNA were extracted from placental tissue using Trizol method, and
reversely transcribed into cDNA using TAKALA reverse transcription kit.
Then, TransStart Tip Green qPCR SuperMIX amplification system and
gene-specific oligonucleotide primers were used to quantify mRNA
expression of BDNF by normalizing the β-action. Each experiment were
performed at least for three times.