The incidence of infants who are large-for-gestational-age (LGA) is on the rise in China, and its detrimental effects on health have received increasing attention. Diet-based interventions have the potential to reduce adverse birth outcomes, particularly in decreasing the occurrence of LGA infants. We aim to evaluate the effect of lipid-focused diet education based on the theories of behaviour change in pregnant women on maternal and offspring outcomes through a randomised controlled trial.

We have designed an open-label, parallel, multicentre randomised controlled trial in collaboration with three hospitals in Beijing, China.

Pregnant women will be recruited before reaching 12 weeks of gestation and will be randomised in a 1:1:1 ratio into three arms: (1) online education arm, (2) pregnancy nutrition checklist and ‘one-page flyer’ arm and (3) routine antenatal education. The primary outcome LGA will be recorded at birth. Demographic information, physical activity, sleep and medical history will be collected through questionnaires and case cards prior to enrolment. Questionnaires will also be used to collect dietary behaviours and psychosocial factors of pregnant women at enrolment, at 24–28 weeks and 34–36 weeks of gestation. Additionally, information on breastfeeding and complementary food supplementation for infants and young children will be obtained through questionnaires. Physical development indicators of children and taste tests will be assessed 3 years after delivery.

The study has received ethical approval from the Capital Medical University Ethics Committee and other collaborating study centres. Informed consent will be introduced to pregnant women, and their consent will be obtained. The findings will be reported in relevant national and international academic conferences and peer-reviewed publications.

ChiCTR2300071126.