I used to work PP at a teaching hospital, that also happened to be the one I had my children.
With my 1st child, I was just out of school, so I didn't know who was who in my room. However, I did have a wonderful med student, Mike, who helped me with counting and holding one of my legs, while pushing. Husband on the other leg. I even threw up on the guy and he took it all in stride! He was great.
My 2nd, I was working there, and during my pregancy, I took care of a pt who requested no one in her room before 7am. She was two days PP, so she had already had her PP labs done the morning before, so her request was appropriate. With that, I hung a sign on her door with her request. This particular time, I was doubling back, and worked the day shift, so I had her the next morning. During report, one of the male med students came in and asked who was taking care of the pt in E338. I told him I was. He asked, "What does this mean?" as he held up the sign that was posted on her door. I told him, "Well, I think it means what it says, no one in the room before 7am," Now mind you, it was already 6:45, so you think this doofus could have gone and done some charting or seen anther pt in that time. But no, against my instructions and the pts wishes, he went in anyway! As a result of this, when I delivered my 2nd child, I told the students they were more than welcome to be in the delivery room with me, however, if at any time they did not respect my wishes, they were gone! Also, because I worked there, I requested no 1st year residents, because we had a real winner of a group that time, and I didn't want any of them near me! I delivered my 2nd fast, my OB hardly made it in time, so seeking out the student was not a conideration.
With my 3rd, I also told the med students my requests, and one of them, female, said to me, "Well, there are somethings we have to do because we have to report to the residents." I told her she didn't need to bother doing the H&P because my priority was my delivery and my baby, not what she had to do for the residents!
Sorry, that was long! You have the right to say no! Don't hesitate to do it!