Antenatal diet and postpartum depressive symptoms: A prospective study
Introduction
Mental health disorders are a leading cause of disability worldwide, and women during the postpartum period are particularly at risk (World Health Organization [WHO], 2008). Perinatal depression, depression that occurs during pregnancy or in the first 12 months following delivery, has been identified as a critical public health concern (Shrivastava et al., 2015, Glavin and Leahy-Warren, 2013). Perinatal depression is one of the most common medical complications in pregnancy and the postpartum period, affecting one in seven women (Committee on Obstetric Practice, 2015). For many women, postpartum depressive symptoms persist for months or even years after giving birthand do not necessarily resolve in the first postpartum year (Woolhouse et al., 2015). Perinatal depression often goes unrecognised because changes in sleep, appetite, and libido may be attributed to normal pregnancy and postpartum changes (Committee on Obstetric Practice, 2015). Left untreated, postnatal depression can have harmful long-term effects on mother and infant, impacting the mother's ability to care for her baby and impeding upon mother-infant attachment (Beck, 1998, Lefkovics et al., 2014, Milgrom et al., 2004). Children exposed to maternal depression are at higher risk of cognitive, social, emotional, behavioural, and developmental problems (Beck, 1998, Kingston et al., 2012, Koutra et al., 2013, Surkan et al., 2011). Therefore, identification of modifiable lifestyle risk factors contributing to postpartum depression is needed.
During pregnancy, women require extra nutrients to support fetal growth and reproductive metabolic needs (Nnam, 2015). Inadequate nutritional intake can result in nutrient depletion and a failure to recover nutritional stores in the postpartum (Gernand et al., 2016). Even though nutritional needs increase during pregnancy, diet quality has been shown to decrease (Moran et al., 2013). Most women are not meeting recommended prenatal nutritional standards, consuming insufficient fruit, vegetables and fish (Blumfield et al., 2012, Blumfield et al., 2013, Hure et al., 2008). A large cohort study of pregnant women found only 6.5% of women met recommendations for vegetable intake, 33% consumed sufficient fruit, and 23% consumed sufficient fish (von Ruesten et al., 2014). Pregnancy has been described as a “teachable moment,” as many women are concerned about the health of their baby, and are open to receiving health advice and making behavioural changes, whilst in frequent contact with healthcare providers (Phelan, 2010). Waiting until after pregnancy to improve diet quality may be too late, particularly as new mothers are less likely to make changes to their diet during this time (van der Pligt et al., 2016). Therefore, although pregnancy is a highly vulnerable time, it is also a prime opportunity to improve maternal diet quality.
In recent years, the link between nutrition and depression has been explored. Nutrition is the foundation of healthy psychological functioning, regulating biological systems that influence mood, including the endocrine systems and neurotransmitter pathways (Leung & Kaplan, 2009). Systematic reviews examining the association between diet quality and depression in non-pregnant populations reported an association between healthy diet and decreased risk of depression (Lai et al., 2014, Quirk et al., 2013, Rahe et al., 2014). Similarly, a systematic review of randomised controlled studies found dietary interventions effective in reducing depressive symptoms (Opie et al., 2014). Crucially, the association between nutrition and depression has also been explored during the perinatal period: a systematic review provided consistent evidence to support a relationship between diet quality during pregnancy and antenatal symptoms of depression (Baskin et al., 2015).
Evidence supporting an association between diet quality during pregnancy and postnatal depressive symptoms is mixed (Baskin et al., 2015). In the Avon Longitudinal Study of Parents and Children, diet quality at 32 weeks gestation, was associated significantly with depressive symptoms between 8 weeks and 33 months postpartum (Barker et al., 2013). Similarly, a health-conscious diet between 14 and 18 weeks gestation was associated significantly with lower postpartum depressive symptoms and a 51% reduced likelihood of experiencing high levels of postnatal depression (Chatzi et al., 2011). In contrast, other studies have not found diet during pregnancy to be significantly associated with postnatal depressive symptoms (Baskin et al., 2016, Okubo et al., 2011, Pina-Camacho et al., 2015). These conflicting results may be due to variation in the way diet quality was measured. Existing studies have used data-driven approaches to characterise dietary patterns, rather than diet quality scores based on existing knowledge of optimal dietary guidelines. Furthermore, existing studies have explored the impact of pregnancy diet on the early postpartum period (Baskin et al., 2015; Chatzi et al., 2011; Okubo et al., 2011). Although two studies have explored the association of pregnancy diet in the postpartum up to 33 months postpartum, these studies were limited as they examined postpartum depressive symptoms as a latent variable (using information on depressive symptoms measured at 8 weeks, 8 months, 21 months, and 33 months postpartum), rather than exploring the association at each time point separately (Barker et al., 2013, Pina-Camacho et al., 2015). It is therefore unclear as to what time point in the postpartum period this association extends. Further research is necessary to determine if improving diet quality, assessed according to existing evidence of optimal dietary requirements during pregnancy, can help to reduce postnatal depressive symptoms in the late postpartum (Michels & Schulze, 2005).
Exploring diet quality by examining intake of specific food groups, is based on existing evidence of what constitutes a healthy diet (McNaughton et al., 2008). Fruit, vegetables and fish, are characteristics common to most healthy dietary patterns (Barker et al., 2013, Baskin et al., 2016, Brantsæter et al., 2014, Chatzi et al., 2011, Okubo et al., 2011, Rahe et al., 2014) and are associated with higher diet quality (Raynor et al., 2011, Schröder et al., 2008). Critically, increased fruit, vegetable and fish intake are associated with lower depressive symptoms in the general population (Akbaraly et al., 2009, Blanchflower et al., 2013, Kingsbury et al., 2016). Although pregnant women are highly motivated to sustain a healthy diet, unfamiliarity with dietary guidelines and lack of nutrition education can prevent adherence to recommendations (Bookari et al., 2016, Lucas et al., 2014). A straightforward description of the recommended number of servings required from each food group to minimise the risk of postnatal depressive symptoms could remove these barriers. Recommendations to increase specific food groups, rather than improve diet quality in general, may be highly valuable as it could be easily understood.
Although there is a clear association between diet quality and depressive symptoms in the general population, the evidence-base exploring this association in the postnatal period is limited. The aim of this study was to examine the association between consumption of food groups characteristic of a quality diet during pregnancy (that is fruit, vegetable and fish intake) and postnatal depressive symptoms up to 12 months postpartum. It was hypothesised that (1) higher fruit, (2) higher vegetable and (3) higher fish intake, measured at 16 and 32 weeks gestation, would be associated with lower depressive symptoms at 12 months postpartum.
Section snippets
Participants and procedure
This study was drawn from a larger study exploring maternal physical and psychosocial wellbeing during pregnancy and the first 12 months post birth. The study began in February 2010 and concluded in January 2014. Eligible women were pregnant, between 10 and 18 weeks gestation, and over 18 years of age. Participants were recruited via advertising on online pregnancy forums, pregnancy and parenting magazines, and two maternity clinics located in metropolitan Melbourne, Australia. Of the 704 women
Participant characteristics
Two hundred and fifty-three participants completed questionnaires at all the required time points. Participant demographic characteristics are presented in Table 1. Mean age was 31.4 years (SD = 4.38; range 21–44). Most participants were married/de-facto (n = 245; 96.8%), were university educated (n = 163; 64.5%), and had an annual family income above $105,000, (n = 133; 53.6%). Fifty (20.7%) participants had a previous diagnosis of depression, which is consistent with the prevalence of
Discussion
The aim of this study was to investigate whether proxy measures of a healthy diet during pregnancy (i.e., fruit, vegetable, and fish intake measured at 16 and 32 weeks gestation), were associated with depressive symptoms at 12 months postpartum. No association between fruit, vegetable or fish intake during pregnancy and postpartum depressive symptoms were found. This has been the first study to measure pregnancy diet by intake of fruit and vegetable food groups, based on existing guidelines of
Limitations
There are several limitations to this study. Participants were composed of a convenience sample, and the study had a high attrition rate, both of which increased the risk of bias on the exposure and outcome measures. A second limitation is that the method used to assess dietary intake was limited to the use of single questions to assess fruit, vegetable and fish intake. Although Oken et al. (2014) found that longer questionnaires added no advantage over a single item questionnaire in measuring
Conclusions and implications for future research
This study did not find an association between fruit, vegetable or fish intake during pregnancy and depressive symptoms at 12 months postpartum. These findings were not consistent with studies that found overall diet quality to be associated with postpartum depressive symptoms (Barker et al., 2013, Chatzi et al., 2011). The following recommendations may contribute to improved understanding of the association between pregnancy diet and postnatal depressive symptoms. (1) Future research should
Acknowledgements
The authors would like to thank the participants for their time and commitment to this research.
Contributions
RG, HS and BH designed the study and analyses, RG conducted the statistical analyses. RG drafted the manuscript with contributions and editing from all authors. CB revised the paper critically for important intellectual content.
Conflict of interest
None declared.
Ethical approval
This study was approved by the Deakin University Human Research Ethics Committee (36-2009 and 2011-087).
Funding sources
BH is funded by a National Health and Medical Research Council Early Career Fellowship (GNT1120477).
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