One universal truth of medicine is that there is no 100% way to avoid injuries, complications, or undesired outcomes. Doctors are also not infallible, so they may make mistakes sometimes or fail to do everything in their power to prevent an injury.
Medical care providers are allowed to be “not perfect”, but what they are not allowed to do is deviate from the “standard of care”.
The legal concept of a “standard of care” comes from many different rules, guidelines, laws, and expectations set by various organizations throughout the medical field. Some standards come directly from regulatory agencies like the U.S. Department of Health, meaning they are essentially laws that must be followed or there could be penalties. Other standards are set by professional organizations that oversee a specific type of practice in a specific area. For instance, a physician helping a patient give birth in Tampa will have standards set in part by the Florida Obstetric and Gynecologic Society. Hospitals and other provider organizations will also set their own standards of care.
You can think of a standard of care as a checklist. So long as your care provider follows everything on the list and does everything they are supposed to, the chances of a birth injury or some other form of harm are minimized. In cases where the standard of care was met (which is always up for debate) but an injury still resulted, it is very possible that the attending physician will not be considered to have committed malpractice because they did everything expected of their profession.
When there is a deviation from the standard of care, however, that means that the provider has opened up the patient to a whole set of risks. Any time a birth injury occurs and the standard of care was clearly not met, the attending physician and their provider organization are supposed to be held liable for the resulting damages.