Objective  To explore the association between serum vitamin D level and the incidence of postpartum depression, so as to provide evidences for prevention of postpartum depression.

Methods  Postpartum women who gave birth and with postpartum examination in Longhua District Central Hospital, Shenzhen, Guangdong Province from September 2020 to September 2021 were assessed by the Edinburgh Postnatal Depression Scale(EPDS) at 42-day postpartum examination, and those with EPDS score ≥ 13 were identified as depression group. One or two postpartum women who addended during the same period, EPDS score < 13, and match the inclusion criteria were selected randomly as control group. Finally 58 women were recruited as case group, while 101 women were recruited as control group. A self-designed questionnaire was used to collect information regarding mode of delivery, social support during the postpartum period, exposure to sunlight, and oral vitamin D supplement. Four weeks after dilivery, 5 mL elbow vein blood specimen was obtained to test serum levels of 25 hydroxy vitamin D25(OH)D and analyze the association between the level of serum vitamin D and the incidence of postpartum depression.

Results  The average level of 25 (OH) D in the control group was (27.45 ± 8.25) ng/mL, which was higher than that in the case group (24.62 ± 8.00) ng/mL(P < 0.05). There was no significant difference between case group and control group in terms of neonatal diseases, neonatal hospitalization, number of people living in a household, main caregiver during the postpartum period, emotional intimacy with husband, calcium supplement during pregnancy and postpartum period, and exposure to sunlight during the postpartum period(P > 0.05). Multivariate analysis showed that compared with postpartum women with adequate 25 (OH) D level, vitamin D deficiency was a risk factor for postpartum depression（OR = 2.40, 95% CI: 1.02 − 5.64）.

Conclusion  Vitamin D deficiency might increase the possibility of postpartum depression incidence. Postpartum women can improve their vitamin D level through appropriate exposure to sunlight and oral vitamin D supplement so as to prevent postpartum depression.