ScopePerinatal maternal moderately high-fat diet (mHFD) is associated with obesity and fatty liver disease in offspring, and maternal fish oil (FO: n-3 PUFA source) supplementation may attenuate these disorders. This study evaluates the effects of FO given to pregnant rats fed a mHFD on the offspring's liver at weaning. Methods and resultsFemale Wistar rats receive an isoenergetic, control (CT: 10.9% from fat) or high-fat (HF: 28.7% from fat) diet before mating, and throughout pregnancy and lactation. FO supplementation (HFFO: 2.9% of FO in the HF diet) is given to one subgroup of HF dams during pregnancy. At weaning, male and female mHFD offspring display higher body mass, adiposity, and hepatic cellular damage, steatosis, and inflammation, accompanied by increased damaged mitochondria. FO does not protect pups from systemic metabolic alterations and partially mitigates hepatic histological damage induced by mHFD only in females. However, FO reduces mRNA expression of lipogenic genes, and mitochondrial damage, and modified mitochondrial morphology suggestive of early adaptations via mitochondrial dynamics. ConclusionsGestational FO supplementation has limited beneficial effects on the damage caused by perinatal mHFD consumption in offspring's liver at weaning. However, FO imprinting effect on lipid metabolism and mitochondria may have beneficial long-term outcomes.