An ultrasound scan using a small probe placed inside the vagina to see the ovaries and uterus clearly.
What the scan is
A transvaginal ultrasound is a scan carried out by a trained clinician, such as a doctor or a sonographer. A small probe covered with a clean sheath is placed inside the vagina, where it sends harmless sound waves that build an image of the ovaries and uterus on a screen. Because the probe sits closer to the ovaries, this scan gives a clearer view than a scan through the abdominal wall. It is a routine procedure in gynaecological assessment, usually takes only a few minutes, and is performed in a controlled clinical setting.
How it relates to PCOS
In a PCOS assessment, a clinician uses this scan to count small follicles and check ovarian volume. The ovary finding is one of the three Rotterdam criteria, alongside androgen signs and cycle pattern. However, the ovary finding alone does not confirm PCOS, because ovaries with many follicles can be seen in some people who do not have PCOS. It is therefore read together with your PCOS symptoms, cycle pattern, and hormone blood tests. The scan is also not a required test for everyone.
Options and comfort
A transvaginal scan is usually not offered to people who have never been sexually active or who are uncomfortable with it. In those situations an abdominal scan is often used instead, although it may give a less detailed view of small follicles. You have the right to ask about the procedure, request an explanation, ask for a chaperone, and state your preferences before the scan goes ahead. The clinician will explain the steps first, and you can stop at any point if you are uncomfortable.
What it means for you
If a doctor suggests this scan, it is usually part of a wider assessment rather than a single test that gives the answer. The scan result is read together with your overall health picture, not on its own. Ask your doctor which scan type suits your situation and what to expect from the result. See also what is PCOS to understand how scan findings fit into the overall picture.
This glossary is education, not diagnosis. For your own situation, ask a doctor or pharmacist.