do they have to do the group B test at 35 weeks? my normal OB is on vacation this coming week so I'm…

do they have to do the group B test at 35 weeks? my normal OB is on vacation this coming week so I'm seeing the other one in the practice (who's a man) for my checkup. I really would rather wait for her to do it at the next appt - which would be 37. I know it's silly, and in about 6 weeks time the whole world will see my lady parts in the delivery room, but for now, I'd rather not have a man doctor do the swab.