Breastfeeding self-efficacy and postpartum depression: a cohort study

ABSTRACT Objective: to evaluate breastfeeding self-efficacy, the presence of postpartum depression symptons and the association between breastfeeding self-efficacy and postpartum depression with cessation of exclusive breastfeeding. Method: cohort study with 83 women. The instruments used were the Breastfeeding Self-Efficacy Scale and the Edinburgh Postnatal Depression Scale. Statistical analysis was conducted using the log-rank tests, analysis of variance and the Cox survival model. Results: breastfeeding self-efficacy (p = 0.315) and postpartum depression (p = 0.0879) did not show any statistical difference over time. The chances of cessation of exclusive breastfeeding decreased by 48% when self-efficacy changed from low to medium and by 80% when it changed from medium to high. Postpartum women who scored ≥10 on the Edinburgh Postnatal Depression Scale interrupt exclusive breastfeeding, on average, 10 days earlier than those with a score ≤9, whose median breastfeeding duration was 38 days postpartum. Conclusion: breastfeeding self-efficacy was proved to be a protective factor for exclusive breastfeeding, while postpartum depression is a risk factor.

Risk factors for PPD are low socioeconomic status, intra-and interpersonal conflicts, and stressful life events, such as health problems and complications in pregnancy, childbirth, postpartum and breastfeeding (11) .
Studies show that women with PPD have less positive interaction with their children, a more negative perception about the child's behavior, an increased risk of early interruption of EBF and a positive association with child malnutrition (5,11,(16)(17) .
The association between breastfeeding and maternal mental health has been confirmed in several studies, despite the inconclusive results regarding the cause-effect relationship. The difficulties in breastfeeding and in the weaning process are some of the causes for the increase in the rates of postpartum depression, confirming the positive influence of breastfeeding in the reduction of PPD symptoms. However, there is a high probability of breastfeeding being affected by postpartum depression (5,(18)(19)(20) .
Considering the relevance of breastfeeding and postpartum mental health for improved rates of infant and maternal morbidity, the following research question

Method
This is a prospective cohort study conducted at the Incentive and Support Center for Breastfeeding and Human Milk Bank, linked to the Federal University of São Paulo, located in the city of São Paulo.
The sample size was calculated considering a 20% incidence of PPD (21) , a 9% error and a 95% confidence limit, resulting in a minimum of 76 participants. The inclusion criteria were women who were exclusively breastfeeding their infants. The exclusion criteria were women who were more than 60 days postpartum at the time of the first interview. from the long-term follow-up, but remained long enough to compose the previous cross-sectional study sample (5) .
In order to prevent early weaning, the breastfeeding clinic conducts monthly consultations, or at shorter intervals when there are complications with the motherchild dyad. The interviews for data collection occurred monthly in the clinic when these women went for their breastfeeding consultations and were conducted by two health professionals previously trained by the researcher.
In case of unavailability to respond to the instruments during their stay in the service, an e-mail was sent with an access link to respond to the instrument via Internet, or telephone interviews were conducted on a day and time previously scheduled. The calls were recorded and the responses transcribed to the instruments by the interviewer.  The Cox proportional hazards survival model was adopted. The BSES and EPDS were considered as covariates and measured at different moments to increase the accuracy of PPD incidence estimates, and data from all women who were followed up for less than 210 days and did not have depression were included.
women. The perception about the relationship with family members was satisfactory in 87.75% of the cases.
The levels of breastfeeding self-efficacy (p = 0.315) and the presence of PPD symptoms (p=0.0639) over time, shown in the graphs in Figures 1 and 2, did not show statistical difference over the months. *Breastfeeding Self-Efficacy Scale

Knowing fragilities' aspects in mothers'
perceptions about their ability to breastfeed is of paramount importance for the establishment and maintenance of breastfeeding, since these aspects can be modified (25)(26) .
The increase in levels of breastfeeding self-efficacy in the first 120 days after delivery, identified in the The decrease in breastfeeding self-efficacy levels 120 days postpartum may be related to the return of these women to work. Considering that 50.72% of the women in this study had formal jobs and were on 120day maternity leave, this data reinforces the negative impact of returning to work on the maintenance of EBF (4,25) . In this study, the chance of interruption of EBF significantly reduced with increasing breastfeeding self-efficacy, decreasing by 48% when moving from low to medium self-efficacy and by 80% when moving from medium to high. Considering that global rates of initiation and maintenance of breastfeeding, more specifically exclusive breastfeeding, are unsatisfactory and that 53% of children under six months are not exclusively breastfed in low-income countries, 61% in lower-middle-income countries and 63% in uppermiddle-income countries, the results of the present study are relevant (2) .
The relationship between breastfeeding and symptoms of postpartum depression seems to be influenced by the woman's intention, during pregnancy, to breastfeed after the child is born. A study that investigated women from gestation until up to 32 weeks postpartum found that non-depressed women who planned to breastfeed were less likely to develop postpartum depression when they were successful in breastfeeding. Thus, not being able to breastfeed as expected increases the risk of PPD (16) .
Other studies indicate that the presence of depressive symptoms in the postpartum period increases the chances of mother-child dyad difficulties in breastfeeding, decreasing maternal confidence in breastfeeding, and increasing the probability of interruption of EBF, confirming the findings of the present study (10,(18)(19)25,28) .

Conclusion
The results show that the chances of cessation of EBF decrease by 80% when breastfeeding selfefficacy changes from medium to high, and by 48% when it changes from low to medium, which demonstrates the existence of a positive association with exclusive breastfeeding. The presence of PPD symptoms presented a statistically significant association (p-value <0.0303) with the cessation of EBF. However, no association was found between the self-efficacy measured by the BSES and the symptoms of PPD measured by the EPDS in the group studied.
Breastfeeding self-efficacy and PPD remained the same in the periods evaluated. Therefore, breastfeeding selfefficacy has been proved to be a protective factor for exclusive breastfeeding, while postpartum depression is a risk factor.