Teen girls are advised to visit an ob-gyn for the first time after turning 13 or after becoming sexually active.

This visit will involve a simple chat with the doctor and often includes no exam. You will meet your doctor, talk to him or her and decide if you’d like to be seen by him/her in the future. 

Sooner or later you’ll need to have a pelvic exam with your ob-gyn. After talking to you and taking your general dimensions, you will have a physical exam.

You will be asked to undress completely and put on a special gown. You will then lay on the examination chair with your legs in the stirrups and knees bent.

At first your doctor will examine the outside of your vagina, then they will check the inside of your pelvic organs using a device called a speculum, which gently hold the vagina open so they can see your cervix and the walls of the vagina.

If necessary, the doctor may also take a swab of tissue to test for inflammation. All this will take around 7 minutes.

You may feel some pressure during a pelvic exam, but it shouldn't hurt.

Remember to relax during the pelvic exam.

An ob-gyn will become an important healthcare provider for you as you mature and they will support you during puberty, making birth control decisions, conception, pregnancy, childbirth, and menopause.

Sources:

What to expect during an ob-gyn visit, webmd.com

Your first gynecologist visit (expecially for teens), acog.org