Abnormalities in early brain development contribute to the etiology of many neurological disorders in later life. Recent advances in genome analysis indicate that large numbers of common gene variants shape any individual's disease risk, including that for major mental illnesses. Polyriboinosinic-polyribocytidilic acid (polyI:C) is known to induce strong innate immune responses that mimic immune activation by viral infections. Our previous findings suggest that activation of the innate immune system in astrocytes results in impairments of neurite outgrowth and spine formation, which lead to behavioral abnormalities in adulthood. Although glial cells are classically thought to provide structural and metabolic support to neurons, they are now widely recognized as essential regulators of neuronal development including neuronal migration, axon and dendrite growth, formation of synapses, and synaptic plasticity. Astrocytes also play critical roles in regulating CNS immune function by responding to inflammatory mediators and producing additional cytokines and chemokines. Most of the functions of astrocytes are mediated by the release of humoral factors through a close interaction with neurons. However, the mechanism by which innate immune activation of astrocytes affects neuronal development remains to be determined. To explore the alteration in proteins secreted from murine astrocytes after polyI:C stimulation, astrocyte-conditioned medium (ACM) was analyzed by 2-dimensional fluorescence difference gel electrophoresis (2D-DIGE). We identified matrix metalloproteinase-3 (Mmp3) as a potential mediator of polyI:C/ACM-induced neurodevelopmental impairment. Here, we provide an overview of the mechanism of neurodevelopmental impairment following polyI:C-induced innate immune activation of astrocytes.