Fetal growth restriction (FGR) is a significant health care issue, affecting 20,000 Australian pregnancies every year. Undetected FGR is one of the key risk factors for stillbirth, but FGR can also cause significant impairments in short and long-term health outcomes for the child. It is a major risk factor for preterm birth and is a recognised causal pathway to the neurodevelopmental injury underlying cognitive and behavioural impairment and cerebral palsy. Current obstetric care is focused on the detection of the growth restricted fetus and then ultrasound assessment of fetal wellbeing to guide timing of delivery. This approach seeks to maximize the gestational age of the fetus at delivery to minimise the risks of prematurity, while delivering the fetus in time to reduce the likelihood of stillbirth. Currently, no therapies exist that can maximize fetal wellbeing in the setting of growth restriction and minimise the frequency of antenatally acquired brain injury due to in-utero hypoxia. This triple-blind, randomized, parallel group, placebo-controlled trial will administer maternal melatonin or placebo supplementation antenatally in the setting of early-onset severe FGR to determine whether melatonin can PROTECT the fetal brain and lead to improved neurodevelopmental outcomes.