A transvaginal ultrasound works by placing a small probe inside the vagina that emits high-frequency sound waves, which bounce off internal organs and return to the probe as echoes. A computer converts those echoes into a real-time image of your uterus, ovaries, fallopian tubes, and cervix. Because the probe sits just centimeters from these structures, it produces sharper, more detailed images than an ultrasound performed through your abdomen.
How the Probe Creates an Image
The probe, called a transducer, is a smooth, narrow wand roughly the width of two fingers. Inside it, a crystal vibrates when electricity passes through it, generating sound waves at frequencies between 5 and 12 megahertz. Those frequencies are far above what the human ear can detect, but they’re ideal for imaging soft tissue at close range. By comparison, the transducer used for a standard abdominal ultrasound typically operates at lower frequencies (2 to 5 megahertz) because the sound has to travel farther through skin, fat, and muscle before reaching the pelvic organs.
When the sound waves hit a boundary between two types of tissue, such as the wall of your uterus and the fluid inside it, some of the energy bounces back. The transducer picks up those returning echoes and sends them to a processor that calculates how far away each boundary is based on how long the echo took to return. The result is a grayscale image updated many times per second, giving the sonographer a live view they can angle and adjust in real time.
What Happens During the Exam
You’ll undress from the waist down and lie on an exam table with your feet in stirrups or your knees bent and apart. The sonographer covers the transducer with a single-use sheath (often a medical-grade condom or a commercial probe cover) and applies a small amount of lubricating gel. The probe is then gently inserted a few inches into the vaginal canal. There is no speculum involved.
Once inside, the sonographer slowly tilts and rotates the wand to capture different angles of your pelvic organs. They’ll typically examine the uterus first, measuring the thickness of the uterine lining and looking for abnormalities, then move the probe to visualize each ovary. The entire exam usually takes 15 to 30 minutes, though a straightforward scan can be finished in under 15.
You’re usually asked to empty your bladder beforehand. Unlike an abdominal ultrasound, which often requires a full bladder to push the intestines out of the way and create an acoustic window, a transvaginal approach doesn’t need that fluid cushion because the probe is already close to the organs. An empty bladder actually gives a clearer view.
What It Feels Like
Most people describe the sensation as pressure rather than pain. In a comparative study published in Ultrasound in Obstetrics and Gynecology, patients rated transvaginal ultrasound at a median pain score of 1.0 on a 0-to-10 scale, making it the least uncomfortable of several common gynecological procedures tested. Individual experiences ranged from 0 (no discomfort at all) up to about 8, so some people do find it more uncomfortable, particularly if they have conditions like vaginismus, pelvic inflammatory disease, or significant tenderness. Communicating with your sonographer helps: they can adjust the angle, slow down, or pause if needed.
What It Can Detect
The high resolution of a transvaginal ultrasound makes it the first-line imaging tool for a wide range of pelvic concerns. It can identify ovarian cysts, uterine fibroids, endometrial polyps, and signs of gynecologic cancers. In early pregnancy, it’s used to confirm whether a pregnancy is developing inside the uterus or in a fallopian tube (ectopic pregnancy), to check for a heartbeat, and to investigate possible miscarriage. Fertility specialists rely on it to monitor follicle development during ovulation induction and to assess the uterine lining before embryo transfer.
One of its more routine uses is measuring endometrial thickness, the lining of the uterus. In someone who is still menstruating, that lining naturally fluctuates from about 3 millimeters just after a period to around 15 millimeters in the second half of the cycle. In postmenopausal individuals, a thickened lining can be a flag for further evaluation. The ultrasound can also confirm whether an IUD is sitting in the correct position.
Why It’s Considered Safe
Ultrasound uses sound waves, not radiation, so it doesn’t carry the risks associated with X-rays or CT scans. The main safety consideration is heat: sound energy absorbed by tissue can cause a slight temperature rise. The American Institute of Ultrasound in Medicine sets guidelines limiting how long the probe should dwell on any one spot based on a measurement called the thermal index. For gynecologic exams where pregnancy is possible, keeping the thermal index at or below 0.7 means there is no recommended time limit at all. Higher thermal index values, which occur mainly in specialized Doppler modes, have progressively shorter recommended exposure times. In a standard diagnostic scan, the thermal index stays well within safe limits throughout the exam.
How the Probe Is Cleaned
Infection control for transvaginal probes follows strict protocols. After every patient, the transducer undergoes high-level disinfection, a process that eliminates virtually all microorganisms. The probe must be cleaned of any residue and dried completely before being treated with a chemical disinfectant or UV-C light. During the exam itself, the single-use sheath acts as a physical barrier. Medical-grade condoms used as probe covers have an acceptance quality limit of 0.25%, meaning fewer than 1 in 400 can have a defect. That standard is ten times stricter than the requirement for standard exam gloves. Newer probe covers with pore sizes under 30 nanometers can block even the smallest viruses, including HPV. Non-latex options are available for people with latex allergies.
Transvaginal vs. Transabdominal Ultrasound
The two approaches complement each other but serve different purposes. A transabdominal ultrasound gives a broader view of the pelvis and is better for surveying large structures or later-stage pregnancies when the uterus has grown well above the pelvic bones. A transvaginal ultrasound excels at fine detail: small ovarian cysts, early pregnancies (before 10 to 12 weeks), subtle changes in the uterine lining, and structures deep in the pelvis that abdominal imaging can’t resolve clearly, especially in patients with a higher body mass index where more tissue sits between the abdominal probe and the organs.
In many cases, a provider will start with a transabdominal scan for an overview and then switch to a transvaginal probe when closer detail is needed. The two exams together give the most complete picture.