Even when parents do leave the room, they can still behave disruptively. In one case, a medical assistant reported that a parent had spied, pressing her ear to the door as I carried on a confidential conversation.
I've also had parents refuse to let their teenager give my office a cellphone number. When we need to speak with such a teen because, say, she tests positive for chlamydia, we've had to get acrobatic by enlisting nurses with youthful voices to call home and pretend to be a girl's friend to try to get her on the phone.
As for the girl who asked for the pregnancy test: When she returned to the exam room, I was faced with an especially tricky situation.
While I continued on my routine consultation, there was a knock at the door. My medical assistant peeked in and asked me to step outside. "Her test is positive."
"Is there an empty exam room I can take her to?" I asked. My medical assistant pointed down the hall and around the corner.
I walked back into the room, practically holding my breath. I looked at the girl, who was sitting on the table, dressed again because we had just about finished. I asked her to follow me outside and to the other room, leaving her mother sitting by herself.
"You're pregnant. Do you know what you want to do?"
She stared at me quietly. Sometimes when I tell a teen this news, she starts to cry. But this time, my patient just looked at me. "No," she said.
"What would you like to tell your mother? I'm sure she is wondering what is going on. I think it would be a good idea if we speak to her together."
"I don't want to tell her anything right now."
"Are you sure? She's probably going to know that the reason we are talking has to do with your pregnancy test. Do you feel unsafe telling her you're pregnant?"
"No. I'll tell her later."
Caught in a pickle between the law and common sense, I walked her back to the room, where her mother waited anxiously. "Is everything okay?"
I answered somewhat stoically. "I'm obligated to protect your daughter's privacy, and she would like what we discussed to remain confidential for now."
The mom protested, but her daughter would not budge. Instead, mother and daughter left, together but entirely separate.
Later I found out that the girl had elected to keep the baby - though, not surprisingly, they found themselves a new personal physician and so we never met again.
One of the promises with adolescent privacy laws, I hope, is to give a girl the space to learn to become a woman. But that day, I worried that the law was getting in the way of that promise, and I questioned its value.
That girl should have told her mother, I kept telling myself.
It would have been better for her, for her developing child and for her relationship with her own mom. To take responsibility for her choice. That would have made her a woman, confidentiality or not.
I've always encouraged teens and their parents to have these conversations openly. Maybe, in the end, that's really the point at which a girl becomes a woman - not when she needs the laws to protect her privacy from her mom, but when she doesn't.
Parikh is a pediatrician in Walnut Creek, Calif. His column appeared in The Washington Post.