Adverse in utero exposures can disrupt fetal brain development, deplete subpopulations of neurons and inhibit formation of normal synaptic connections. A major roadblock to unraveling the precise mechanisms and timing of human neurodevelopmental derangement is the almost complete absence of sensitive noninvasive assessments. We present novel methods for isolating fetal neuronal exosomes from maternal plasma as a noninvasive platform for testing aspects of fetal neurodevelopment as early as the 1st trimester. Our methodology represents an important breakthrough both in understanding mechanisms of injury in vivo in a human system and potentially for monitoring clinical interventions seeking to promote fetal brain health.