2.3 Reverse transcription PCR
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.