Developing neurons synthesize substantial quantities of membrane phospholipids in producing new synapses. We investigated the effects of maternal uridine (as uridine-5′-monophosphate) and docosahexaenoic acid supplementation on pups' brain phospholipids, synaptic proteins and dendritic spine densities. Dams consumed neither, 1 or both compounds for 10 days before parturition and 20 days while nursing. By day 21, brains of weanlings receiving both exhibited significant increases in membrane phosphatides, various pre- and postsynaptic proteins (synapsin-1, mGluR1, PSD-95), and in hippocampal dendritic spine densities. Administering these phosphatide precursors to lactating mothers or infants could be useful for treating developmental disorders characterized by deficient synapses. Copyright © 2009 S. Karger AG, Basel.