Objective To determine the role of carotid sinus innervation on differential fetal organ growth during maternal nutrient restriction in late pregnancy.Design Randomised controlled study.Setting University research facility.Sample Thirty-nine Merino ewes.Methods At 113 days gestational age (dGA), fetuses were bilaterally carotid sinus denervated or sham denervated. From 118 dGA, the surgery groups were subdivided into two dietary groups, and their ewes were fed 100% of nutrient requirements or 50% until tissue collection at 1,10 dGA. This provided four groups (sham/control diet, sham/restricted diet, denervated/control diet and denervated/restricted diet).Main outcome measures Fetal organ weights and hormone levels and maternal weight change during the dietary restriction.Results Adrenal glands were larger in sham/restricted diet fetuses than in sham/control diet or denervated/restricted diet fetuses (P < 0.05). Fetal adrenal weight and brain-to-liver weight ratio were positively related to maternal weight change during the nutritional challenge in sham fetuses only (P < 0.05). Fetal liver weight was negatively related to maternal weight change during nutritional challenge in sham fetuses only (P < 0.05).Conclusions We have shown a reduction in liver growth but sparing of adrenal growth in response to moderate maternal undernutrition, which is dependent on intact carotid body innervation. This suggests a new role for the carotid bodies in the control of differential organ growth during such undernutrition.