Breastfeeding and its impact on womens’ health

Breastfeeding has a huge effect on the physiology of the breastfeeding woman. Just how great an effect this is has only started to become apparent in the past few decades, as we learn more and more about the many health benefits for both mother and her infant. (Victora et al., 2016). Pregnancy, particularly complicated pregnancy, is associated with detrimental effect on the mother’s health for many years postpartum (McNestry et al., 2023). Conversely, breastfeeding is an important risk mitigating behaviour for women at risk of non-communicable disease. It is especially valuable as an intervention as it is low cost and accessible to women of all socio-economic backgrounds in all nations. Women with overweight and obesity are at risk of reduced breastfeeding success due to physical and psychological barriers associated with their body habitus. The association between breastfeeding and reduced risk of type 2 diabetes is well established (Aune et al., 2014), but more recently a link between breastfeeding and cardiovascular risk has been confirmed by systematic review (Tschiderer et al., 2022). Potential underlying mechanisms suggested include the physiological effects of the lactation hormones, a “resetting” effect of lactation on maternal metabolism, and improved postnatal weight loss, but as yet these have not been fully established. To date, few studies have examined breastfeeding and later maternal inflammatory markers. A small number of studies have suggested that there is a relationship with between lower visceral fat and previous breastfeeding. The first half of this thesis discusses the Latch On Study, which was a multicentre randomised controlled trial of a multicomponent breastfeeding support intervention for women with BMI >/= 25 kg/m2. We found that the multicomponent breastfeeding support intervention was not associated with increased breastfeeding rates at any timepoint (O’Reilly et al., 2024). Surprisingly high breastfeeding rates, 50% higher than local rates in each study centre, were found in the control group. Participant self-selection, the Hawthorne effect and other factors may have had an influence on outcomes. The control group accessed more private lactation support, whereas the intervention group accessed more in-hospital support. We also performed a mixed-methods process analysis of the Latch On Study. We found the intervention to be low-cost at €157.00 per participant, although full cost-effectiveness analysis could not be completed. The intervention was delivered with fidelity and positively impacted the experience of establishing breastfeeding in the intervention group, but this did not translate to improved breastfeeding rates. The second half of this thesis explores the relationship between lifetime breastfeeding and cardiovascular risk markers, and breastfeeding and depression and anxiety, at 9-11-years postpartum in 168 later reproductive age women from the ROLO Longitudinal Birth Cohort. We found that breastfeeding was associated with lower fat mass, percentage body fat and visceral fat volume after controlling for Body Mass Index (BMI) and other confounders. This adds to the evidence that breastfeeding has a more subtle association with body
composition than was previously thought. Glycoprotein Acetyls (GlycA) is a novel inflammatory marker associated with cardiovascular risk. We examined the relationship between breastfeeding and GlycA as well as more established risk markers including c-reactive protein and interleukin-6. We found that breastfeeding is associated with GlycA – suggesting a potential inflammatory pathway by which later risk could be mitigated. Inflammation is also associated with type 2 diabetes mellitus, so again this is suggestive of a potential risk reduction mechanism. We also found that breastfeeding was not associated with later cardiovascular risk scores, lipid profile, blood pressure or other measurements of body composition and anthropometry. Our analysis found an association between longer breastfeeding and lower depression and anxiety in this cohort. Breastfeeding is known to be associated with lower postnatal depression (Alimi et al., 2022; Xia et al., 2022) but few studies have examined the association in the longer term. As far as we are aware, this is the first report of such an association in this age group. Further studies are required to confirm the findings. The results of the Latch On study have shown that breastfeeding support of any form is important for breastfeeding success in women with overweight and obesity, although we did not find this specific intervention to be superior to usual care. We have also expanded on the existing literature, demonstrating the association of breastfeeding with later body composition, inflammation and mental health outcomes. Supporting breastfeeding is essential for improving population health in the years to come.

Author and appendices