The protective mechanism seen for women delivering in winter and spring may be attributed to the seasonal enjoyment of indoor activities mothers experience with newborns, the researchers said.
Further, the findings showed that women who delivered babies at a higher gestational age (along in their pregnancy) were less likely to develop postpartum depression.
Conversely, women who did not have anaesthesia may have been at an increased risk of postpartum depression.
It is because the pain associated with labour may have been traumatising to the women during delivery.
In addition, increased body mass index (BMI) was also associated with an increased risk of postpartum depression, said researchers while presenting the results at the ANESTHESIOLOGY 2017 annual meeting in Boston.
"We wanted to find out whether there are certain factors influencing the risk of developing postpartum depression that may be avoided to improve women's health both physically and mentally," said lead author Jie Zhou, MD at the Brigham and Women's Hospital in Boston.
Postpartum depression typically arises from a combination of hormonal changes, psychological adjustments to motherhood and fatigue.
Symptoms of postpartum depression include sadness, restlessness and/or agitation and decreased concentration.
At least 10 percent of women suffer from anxiety or depressive disorders following childbirth.
For the study, the team included a review of medical records of 20 169 women who delivered babies from June 2015 through August 2017. A total of 817 (4.1 percent) women experienced postpartum depression.