BDNF and depressive symptom measurement: As shown in the bottom panel of Table 3, compared with BDNF levels in the highest quartile (>25.31 ng/ml), women with lower levels (≤25.31 ng/ml) had a 1.61-fold higher odds of antepartum depression (OR = 1.61; 95% CI: 1.13-2.30) after adjustments for confounding factors including maternal age, parity and early pregnancy body mass index.