The doctor-patient relationship is always based on the level of comfort because you're going to entrust your life and the baby's to the doctor. You must feel comfortable. If you're not comfortable, there's no harm in changing. Most people would not change because the doctor already know you and you have built up with certain rapport. Should you think there is a need to change for whatever reason (e.g you may not agree to do a c-section but the doctor offers), you can always seek another opinion and see whether you're comfortable with the other doctor.