Retained Reflexes - What is it and how does it affect children? Primitive Reflexes develop in the brain stem before birth and are necessary for our ability to navigate the birth process, the first breath, feeding, urination, survival, and development. Plus! Take the free BrainGut Blueprint™, a 10-minute self-assessment that shows where your sensory, gut, sleep, energy, and immune systems are under the most strain right now.