Linking two randomised controlled trials for Healthy Beginnings©: optimising early obesity prevention programs for children under 3 years.

Background: Beginning in 2017 we have conducted a 3-arm randomised controlled trial (RCT) to determine the effectiveness of an early obesity intervention in the first two years of life using either telephone or Short Message Service (SMS) support for mothers. The trial recruited 1155 mothers from their third trimester of pregnancy. This protocol is for a new trial to build on the existing trial using the mother-child dyads retained at 24 months for recruitment to the new RCT. The aim of this new trial is to test whether use of a combination of telephone and SMS interventions is effective in promoting healthy eating and physical activity, as well as reducing child body mass index (BMI) at 3 years of age.

Methods: We will conduct a parallel RCT with an estimated sample of 750 mother-child dyads retained from the existing trial at 24 months. Mothers who completed the 24 months survey, including a telephone survey and measurement of child's height and weight will be invited to participate in the new trial. Informed consent will be obtained at the 24 months survey. The participating mother-child dyads will then be randomly allocated to the intervention (combined telephone and text messaging intervention) or the control group. The intervention will comprise three staged telephone consultations and text messages after each of the three intervention booklets is mailed to mothers at specific time-points between two and three years of child age. The main trial outcome measures include a) BMI and BMI z-score measured at 36 months, b) diet, physical activity and screen time c) cost-effectiveness, and d) feasibility and acceptability of the intervention.

Discussion: This unique opportunity to link two studies will expedite project start up time, utilise existing research infrastructure and systems to run the study, and optimise the use of an already engaged population of study participants. It can address a significant knowledge gap regarding early obesity prevention for children aged 2 to 3 years. The feasibility and effectiveness of the combined telephone and SMS intervention will indicate whether this is a scaleable, broad-reach and low-cost early obesity intervention.

Trial Registration: The trial was registered with the Australian Clinical Trial Registry ( ACTRN12618001571268 ) on 20/09/2018.