It depends on whether you are a full-time or part-time reservist at the time you apply for maternity leave. As a part-time reservist, you must maintain your civilian medical care. If you're a full-time reservist for a period of more than six months, that is, if you're on a term of employment, then you will receive medical care that is comparable with that of the regular force.
Again, there are differences. Not all reservists would receive full and comprehensive Canadian Armed Forces medical care, nor do regular forces as well. Because of the special nature of some pregnancies, they are often offered civilian expertise or access to civilian care.
For part-time class A reservists, the majority of reservists, they have to maintain their provincial health care and their own doctor, so they aren't provided with medical care in that case for maternity.