3.2 Genetic analysis
The genotype distribution of the site conformed to genetic balance and had a better population representation through Hardy-Weinberg equilibrium test. As Table 2 showed,the locus allele of BDNF Val66Met was significantly different between the case group and the control group, and the difference was statistically significant(χ2=4.657, P=0.031, OR=0.884, 95%CI=0.791-0.989), suggesting that allele G may play a protective role in the occurrence of PE. However, the genotype distribution is no significant difference(χ2=4.555, P=0.103) between two groups. There was no significant difference between the two groups in additive gene analysis (χ2 = 2.682, P = 0.102, OR = 0.856, 95% CI = 0.710-1.031).