Background: Childhood is an important age for growth and continuing development. Early investment, especially during pregnancy increases quality antenatal care and can prevent complications, providing the child with their highest health potential for the future. In Thailand, pregnant women will receive the maternal and child health handbook (MCHH), a comprehensive guide used for recording and communicating important health information between the pregnant woman and health care provide (HCP), from pregnancy till the child is 6 years old. Despite the potential, not so many people read the MCHH, many hold the misunderstanding that the MCHH is for communication between HCPs. As a hardcopy, the MCHH bears a printing cost, once provided to the user, the content and functions cannot be upgraded simultaneously, and is at risk for wear and tear or loss of the book. KhunLook mobile application (KhunLook app) was developed in 2015 for parents, childcare providers, and HCPs to use as an interactive electronic MCHH intended to assist parents in child health supervision from 0-18 years. The content can be easily updated, data can be backed, minimizing the risk of loosing data. KhunLook application is found to be well accepted and easy to use. Using KhunLooK application can also increase parent health literacy. Currently, KhunLook app has been downloaded more than 550,000 times. KhunLook yields potential for further development of a maternal mode for pregnant women, for even more potential of Thai people. Objectives: We aim to develop the maternal mode of KhunLook app for promotion of Maternal and child health then to pilot the use of the application at the antenatal clinic in 2 groups of users, pregnant women, and HCPs. Methods: This study has 2 phases 1) Development of KhunLook maternal mode and 2) Pilot use of KhunLook maternal mode at the antenatal care clinic. The study was conducted during August 2021 to May 2023, we studied user requirements and incorporated feedback from pregnant, post partum women and HCPs who provide antenatal care. Content was developed and verified by maternal-fetal medicine specialist. Then the final application was piloted at the antenatal care clinic Srinagarind hospital and the Faculty of Medicine, Khon Kaen University. Ethics approval for this study was obtained from the Research Ethics Committee, Khon Kaen University.Results: Development of KhunLook Maternal mode. After brainstorming within the team for a prototype, the prototype was presented to participants for user requirements and feedback. Eighteen pregnant and post-partum women, and 27 HCPs participated in this phase of the study. The functions within the app and the content were well accepted for usefulness and understandability, the app was easier to use than the MCHH. The content was rated good to very good by the specialists. We incorporated the suggestions and feedback to develop the final application and tested it for functionality. The final application had a family, gestational age, information, health records, and a summary page. Pilot use of KhunLook maternal mode at the antenatal clinic. Forty-five pregnant women and 13 HCPs participated in this phase. The pregnant women’s mean age was 30.1 (20-40) years, and 33.3%, 31.3% and 35.6% were in their 1st, 2nd and 3rd trimester of pregnancy. The HCP’s mean age was 44.4 years. All the participants rated the functions and content to be very good and good. The app was rated easier to use than the MCHH on all items, with statistical significance on all items for pregnant women, and for some items for the HCPs. Users rated the app 9.0 and 8.7/10 versus 7.5 and 7.9/10 for the MCHH, which was statistically significant in both user groups (p=0.000, p=0.0205). KhunLook is intended to be complementary to the MCHH, but if only 1 mode was to be chosen, 86.7% of pregnant women and 30.8% of HCPs chose KhunLook app over the MCHH. Pregnant women stated that they preferred KhunLook due to the ease of use, completeness, and understandability of the content, and since they already have a mobile phone, there is no hassle of carrying a book around. Those who weren’t sure which mode to pick stated that they were worried that the information could be lost and preferred to use both methods together. All HCPs would introduce KhunLook app to their patients because it has quality information, it is very useful, convenient, easy to use. The maternal mode of KhunLook app is well accepted, in pregnant women and HCPs. We suggest using it in complementary of the MCHH. More promotion is needed for its use to reach potential.