Informed consent is when a medical provider informs the patient about the potential risks, benefits, and alternatives in a given medical procedure or intervention. Although it results in a patient's authorization or agreement to proceed, it doesn't release the physician or other medical provider from medical negligence.
Even if you signed a consent form, you may still be able to recover compensation for Erb's palsy. But you must establish that the medical provider didn't meet the applicable standard of care while treating you, causing your injury and losses.