INTRODUCTION:Despite recommendations that pregnant women increase their docosahexaenoic acid (DHA) intake to support fetal brain development, a recent systematic review found a lack of high-quality data to support the long-term effects of DHA supplementation on children's neurodevelopment. METHODS AND ANALYSIS:We will assess child neurodevelopment at 7 years of age in follow-up of a multicentre double-blind randomised controlled trial of DHA supplementation in pregnancy. In 2010-2012, n=2399 Australian women with a singleton pregnancy <21 weeks' gestation were randomised to receive 3 capsules daily containing a total dose of 800 mg DHA/day or a vegetable oil placebo until birth. N=726 children from Adelaide (all n=97 born preterm, random sample of n=630 born at term) were selected for neurodevelopmental follow-up and n=638 (preterm n=85) are still enrolled at 7 years of age. At the 7-year follow-up, a psychologist will assess the primary outcome, IQ, with the Wechsler Abbreviated Scale of Intelligence, Second Edition. Specific measures of executive functioning (Fruit Stroop and the Rey Complex Figure), attention (Test of Everyday Attention for Children), memory and learning (Rey Auditory Verbal Learning Test), language (Clinical Evaluation of Language Fundamentals, Fourth Edition) and basic educational skills (Wide Range Achievement Test, Fourth Edition) will also be administered. Caregivers will be asked to complete questionnaires measuring behaviour and executive functioning. Families, clinicians and research personnel are blinded to group assignment with the exception of families who requested unblinding prior to the follow-up. All analyses will be conducted according to the intention-to-treat principal. ETHICS AND DISSEMINATION:All procedures will be approved by the relevant institutional ethics committees prior to start of the study. The results of this study will be disseminated in peer-reviewed journal publications and academic presentations. TRIAL REGISTRATION NUMBERS:ACTRN12605000569606 and ACTRN12614000770662.