Objectives To assess the impact of prenatal and postnatal family support on the association between infant sex and postpartum depression (PPD).

Design Prospective cohort study.

Setting Pregnant women seen at Hunan Maternal and Infant Hospital, the First Affiliated and the Third Affiliated Hospitals of the Central South University in Changsha, Hunan, People's Republic of China from February to September 2007.

Participants 534 Pregnant women who were consecutively recruited from the participating hospital during their prenatal visits at 30–32 weeks of gestation and who completed the 2 weeks postpartum survey, with no recorded major psychiatric disorders and obstetric and/or pregnancy complications.

Main outcome measure PPD, which was defined as a score of 13 or higher of the Edinburgh Postnatal Depression Scale.

Results Postnatal family support scores were much lower in women who gave birth to a female infant, and the OR of PPD was 3.67 (95% CI 2.31 to 5.84) for them as compared to women who gave birth to a male infant. After adjusting by postnatal support from all family members, husband and parents, the ORs of PPD for women who gave birth to a female infant decreased to 2.06 (95% CI 1.20 to 3.53), 2.89 (95% CI 1.76 to 4.77) and 2.20 (95% CI 1.28 to 3.77), respectively.

Discussion Increased risk of PPD in Chinese women who gave birth to a female infant can be explained to large extent by inadequate or poor postpartum support from family members, particularly husband and parents.