It is well recognised that breastfeeding is extremely beneficial for child survival, growth, and maternal health and is one of the most effective health interventions for preventing infant and child mortality and promoting lifelong maternal health. In addition, breastfeeding provides significant economic benefits and improves health equity in society. In Hong Kong, data from 2021 shows only 22% of women exclusively breastfeed until six months postpartum, significantly less than both the average global rate of 38% and the World Health Organization (WHO) 2025 target of 50%. Some of the common reasons cited by mothers for early weaning relate to breastfeeding problems that are easily avoided with appropriate early professional support, such as perceived insufficient milk, poor latching and sore breasts. Timely breastfeeding support could therefore promote exclusive breastfeeding. However, such support is often inadequate and has been difficult to obtain during the recent COVID-19 pandemic. In addition, mothers in Hong Kong may find it difficult to leave home during the early postpartum period due to the overwhelming workload and the cultural tradition practice of 'doing the month' in which women remain housebound during the first month postpartum. Therefore, it is be important to provide adequate support to mothers in Hong Kong to ensure that breastfeeding can continue for the optimal duration, thereby providing life-long protection for both mother and infant.

Social cognitive theory (SCT) is widely used to analyse behavioural changes in breastfeeding in response to technology-guided interventions. We will use SCT as a theoretical framework to guide the development of a message library and the delivery of both regular and chat-style support messages. The increased accessibility of an Internet-delivered intervention provides a way to promote each mother's sense of agency by enabling them to access the support they require when they need it. As more people turn to eHealth, the development of an Internet-delivered SCT-based intervention (iSCT-I) to support and educate women may provide a cost-effective way to increase breastfeeding rates. Moreover, the WHO has concluded that will not be possible to reach universal health care coverage without investing in, and broadly adopting, eHealth. EMI is a cost-effective intervention framework that allows personalisation of both the content and delivery method, it can therefore provide a practical and effective strategy for delivering iSCT-I for improving breastfeeding duration and uptake. However, there have been no previous studies of EMI-based breastfeeding interventions. Therefore, we propose an RCT to evaluate the effectiveness of EMI-delivered iSCT-I; a real-time, personalized, and cost-effective approach for improving exclusive breastfeeding rates.

This multi-center randomized control trial adopts two arm design to examine and compare the effects between ecological momentary intervention and usual care to improve breastfeeding outcomes. The study hypotheses are (1) Primiparous mothers who receive an EMI-based breastfeeding intervention will significantly increase their exclusive breastfeeding intention and duration, and (2) The intervention group will have a higher breastfeeding self-efficacy score (BSES) and breastfeeding knowledge and attitude scores at three months postpartum.

A pilot study will be conducted. Aiming to recruit 20 participants. (10:Intervention; 10 Control)