The Influence of a Dietary Intervention on Postnatal Mental Health and Well-Being: A randomised controlled trial among pregnant women living with obesity in the Counties Manukau Health region, South Auckland

Abstract

Background: Maternal mental health concerns, such as perinatal depression and anxiety are common during pregnancy and after birth. Depression and anxiety have been associated with a range of adverse outcomes for the mother, her child, and the wider family. Maternal obesity is another prevalent health condition that is related to a range of adverse health outcomes and can increase the risk for mental health concerns. In the Counties Manukau Health (CHM) district in South Auckland, New Zealand there is a high percentage of women entering pregnancy while living with obesity, and this rate continues to rise. Moreover, a substantial percentage of pregnant women in the CHM region experience high levels of socioeconomic deprivation and belong to ethnic minority groups, which may increase the vulnerability of these women to experience maternal mental health concerns. One approach to target both mental health concerns and obesity is through a dietary intervention. There is a growing body of evidence on the therapeutic effects of dietary intervention on mental health. So far, few studies have explored the influence of a dietary intervention on mental health outcomes in a population of pregnant or postpartum women living with obesity. Aim: This study investigated the influence of a dietary intervention on postnatal mental health outcomes among a multi-ethnic sample of pregnant women living with obesity in the CHM region in South Auckland, New Zealand. The study also aimed to examine the rate of depression in the postpartum period within this population, and to explore body mass index (BMI), history of depression, deprivation, and ethnicity as contributory risk factors for depression, with a secondary aim of exploring the influence of probiotics on postnatal mental health outcomes. Methods: The current study was conducted as a sub-study of the larger Healthy Mums and Babies (HUMBA) trial, which was a single-centre, two-by-two factorial (parallel groups) design randomised controlled trial conducted in South Auckland. A total of 230 women were recruited within the CHM region between April 2015 and June 2015, and then randomised into either the dietary intervention or the routine advice group, in addition to receiving either a probiotic or a placebo capsule. The dietary intervention consisted of a handbook covering topics, such as portion size, healthy recipes, and ways to stay active, alongside four home-based education sessions lead by a trained community worker. Maternal mental health outcomes including depression, anxiety, and quality of life (functional health and well-being) were assessed at baseline (12-17 weeks’ gestation) and 4-6 months postpartum. Primary outcome data (depression scores at 4-6 months postpartum) were attained for 161 women. Results: Statistical analyses revealed that the dietary intervention did not significantly improve depression, anxiety or functional health and well-being scores from baseline to 4-6 months postpartum compared to the routine advice group. However, depression scores did improve over time for both the dietary intervention and routine advice group. Anxiety scores increased (i.e., worsened) over time, regardless of group allocation, and anxiety scores increased more in the dietary intervention comparative to the routine advice group. Physical functioning scores improved between baseline and 4-6 months postpartum, irrespective of group allocation. Mental functioning scores did not improve for either the dietary intervention or routine advice group or over time. Exploratory analyses found that the probiotic intervention did not significantly improve maternal mental health outcomes compared to placebo. In terms of risk factors, only history of depression was found to be associated with depression scores at 4-6 months postpartum with BMI, deprivation, and ethnicity not significant. The rate of depression in the sample at 4-6 months postpartum was 13%. Conclusion: The findings suggest that neither the dietary intervention nor the probiotic intervention had any beneficial effects on mental health outcomes in this sample of women compared to routine care/placebos. This study accentuates the need for further randomised controlled trials of dietary interventions in this population and the need to specifically target psychological outcomes and to explore timing of dietary interventions for postpartum women living with obesity. This study's findings have provided a valuable and essential contribution to the literature on the role that diet has on mental health, particularly within a unique multi-ethnic sample characterised by pregnancy, obesity, and high deprivation.