Relationship between postpartum depression and lactation status at a Japanese perinatal center: A cross-sectional study

Introduction

Exclusive breastfeeding for the first 6 months of life has been recommended because of important health, medical, social, and developmental benefits to both mothers and babies¹. Postpartum depression has been recognized as the leading medical complication among new mothers^2,3. To date, some risk factors for postpartum depression, such as personal and family factors, socioeconomic status, support from other family members and personal plans for furthering careers, have been examined^4–8. Some studies have demonstrated that breastfeeding can protect mothers from postpartum depression and are starting to clarify which biological and psychological processes may explain this protection^9–11. In addition, a short duration of breastfeeding has been reported to be associated with the development of postpartum depression¹¹.

In Japan, the breastfeeding rate at Japan’s baby-friendly hospitals (BFHs) at one month of age has been reported to be more than 75%¹²; however, inconsistent knowledge of breastfeeding benefits and inappropriate hospital practices has been reported to be associated with the increased use of infant formula and reduced breastfeeding duration, although the national breastfeeding rates had been higher than other countries of similar health status¹³. Unfortunately, only 50% of women who delivered at Japanese Red Cross Katsushika Maternity Hospital, a non-BFH institute, have performed exclusive breastfeeding for their babies at one month after delivery^14,15. Recently, in Japan, the population of elderly and/or high-risk pregnant women has been increased, and the rate of exclusive breastfeeding may be expected to decrease⁴. To examine the necessity of breastfeeding promotion in relation to maternal mental status, we examined the association between lactation status and postpartum depression at one month after delivery in Japanese women.

Methods

The protocol for this analysis was approved by the Ethics Committee of the Japanese Red Cross Katsushika Maternity Hospital (approval number, K2018001). Written informed consent was obtained from each woman to participate in this study at the first meeting, i.e. before birth.

Results

On admission, 592 women (73.1%) hoped to perform exclusive breastfeeding for their babies and who met the conditions to be considered in the current study. Of these, 442 (74.7%) performed exclusive breastfeeding at one month, while 150 (25.3%) performed mixed or artificial feeding (mixed feeding: 296, artificial feeding: 24). There were no significant differences in maternal age between the two groups (exclusive breastfeeding: 32.4 ± 6.1 years; mixed or artificially feeding: 32.8 ± 6.4 years; p = 0.11).

The average EPDS scores and the incidence of EPDS scores of ≥9 points in the women performing exclusive breastfeeding were 4.3 ± 3.6 and 14.3% (63/442), respectively. These did not differ from those in the women performing mixed or artificial feeding [4.2 ± 3.7, p = 0.60 and 13.3% (20/150), p = 0.78]. In addition, the average EPDS score and the incidence of EPDS scores of ≥9 points in the women performing exclusive artificial feeding was 4.0 ± 3.2 and 8.3% (2/24), respectively.

Discussion

The current results seemed to be contrary to those in some previous studies indicating that breastfeeding can protect mothers from postpartum depression^9–11. In this study, a trend of higher score of EPDS was observed in the women with exclusive breastfeeding group, though the results were non-significant. The current results seemed to be unpredictable for us.

To date, lower plasma oxytocin levels leading to incomplete breastfeeding have been reported to be associated with the development of postpartum depression. In a recent study by Lara-Cinisomo et al.¹⁰, for example, lower levels of plasma oxytocin were observed in women who had stopped breastfeeding and had postpartum depression by two months postpartum. The influence of synthetic oxytocin on a new mother’s well-being has been also reported previously^10,21,22. Oxytocin is released across the breastfeeding cycle, and oxytocin release has observed to exhibit a temporary anxiolytic-like calming effect on postpartum maternal mood disturbances²¹. Therefore, oxytocin is believed to mediate a calming effect on postpartum mood in primiparous mothers with breastfeeding.

However, in this study, exclusive breastfeeding did not contribute to the prevention of postpartum depression significantly. The mental status of mothers considered to have low levels of oxytocin associate with incomplete breastfeeding seemed to be stable. Therefore, in social environments and/or clinical characteristics of pregnant Japanese women, there may be some serious risk factors for postpartum depression other than the status of breastfeeding, such as personal and family factors, socioeconomic status, support from other family members and personal plans for furthering careers^4–8. For example, in our recent Japanese study that asked mothers’ biggest worry at two weeks after delivery, only 10% reported anxiety about breastfeeding⁸. Although we believe that Japan is not a poor country, recently there are some morbid pregnant women who have been reduced to poverty²³.

We understand the small sample of the current study is a serious limitations. A study in women who gave birth at BFHs may have totally different results than the current results. In this study, although we excluded the cases reported to be associated with the prevalence of exclusive breastfeeding and/or postpartum depression^4,11,16–18 to control confounding factors, we did not perform a further detailed comparison of the women’s characteristics. In addition, although the EPDS has been the most widely used screening tool for postpartum depression in maternity and child services in various countries throughout the world, a EPDS high score does not mean the presence of postpartum depression^19,20,24,25.

In conclusion, development of postpartum depression does not seem to be associated with incomplete breastfeeding in Japanese women at our institute. Consequently, there must be other risk factors associated with the development of postpartum depression. A further larger study is needed to clarify these factors.

Data availability