In Ontario, you can choose an obstetrician, family physician or registered midwife to care for you in pregnancy and attend your birth, though choices may be limited in some communities. Some nurse practitioners and registered nurses do prenatal and postnatal care, also.
Each type of maternity care provider has their own scope of practice and on-call schedule. It's best to start prenatal care as early as possible and to find a maternity care provider that's the right match for your needs. Your care provider's hospital privileges determine which hospital you'd go to and some of your options like choice of birth place are dependent on whether you're with a midwife or not. If you're interested in a birth centre or home birth, find out early whether that is an option with your maternity care provider. Do not hesitate to see more than one provider before you decide what's best for you.
Here are some resources that can help you make your choice including information on the scope of practice and roles of each provider, and questions to consider when making your choice.