This was predicted. No doctor is taking a chance to be arrested or sued, let alone losing their license to practice medicine in the state.
It doesn't just affect OBs or gynecologists. A general practitioner or an emergency room doctor could prescribe a medication and if that patient happens to be pregnant (and did not know it at the time she received the medication) and has a miscarriage due to the medication, that doctor could go to jail and be sued by every family member of the patient. It's common sense that they would move to states where abortion is legal and where they can provide the standard of care they were trained to provide, without fear of being arrested or enormous legal fees.