A transvaginal (TVS) ultrasound is an imaging exam where a small, thin probe is inserted into the vagina to create detailed pictures of the uterus, ovaries, cervix, and surrounding pelvic structures. Unlike a standard abdominal ultrasound, the probe sits much closer to these organs, producing sharper images that help diagnose conditions ranging from ovarian cysts to early pregnancy complications. The exam typically takes 15 to 30 minutes.
How It Works
The probe, sometimes called a transducer, emits high-frequency sound waves that bounce off your internal organs and return to the device. A computer translates those echoes into a real-time image on a screen. Because the probe sits just centimeters from the uterus and ovaries rather than sending sound waves through the abdominal wall, it operates at higher frequencies (5 to 7.5 MHz compared to 3 to 5 MHz for an abdominal scan). Higher frequency means finer detail, which is why TVS is the preferred method for evaluating most pelvic concerns.
Why TVS Produces Better Images
A transabdominal ultrasound has to push sound waves through skin, fat, and muscle before reaching the pelvic organs. That journey degrades the image, especially in people with a higher body weight or significant bowel gas. TVS bypasses all of that. In a study comparing the two approaches for evaluating pelvic masses, the transvaginal images provided more diagnostic detail in 76% of patients. The abdominal scan didn’t outperform TVS in a single case. Ten masses, including both simple cysts and complex growths, were only visible on the transvaginal images.
What It’s Used to Diagnose
TVS is one of the most versatile tools in gynecologic imaging. Common reasons your provider might order one include:
- Abnormal bleeding: heavy periods, irregular cycles, bleeding between periods, or bleeding after menopause
- Pelvic pain or cramping: evaluating for fibroids, ovarian cysts, or endometriosis
- Early pregnancy: confirming the pregnancy is in the uterus, checking for ectopic pregnancy, or evaluating a possible miscarriage
- Infertility: assessing ovarian follicles, uterine shape, and endometrial lining during fertility treatment
- Pelvic masses: determining whether a lump is a fluid-filled cyst, a solid growth, or something more complex
Beyond gynecologic concerns, TVS can also evaluate nearby structures like the bladder, lower bowel, and pelvic blood vessels. It’s frequently used to guide procedures such as egg retrievals during IVF or biopsies of the uterine lining.
Measuring the Uterine Lining
One of the most common things TVS measures is endometrial thickness, the lining of the uterus. This measurement changes throughout the menstrual cycle: it’s as thin as 1 to 4 mm during a period, grows to 12 to 13 mm around ovulation, and reaches 16 to 18 mm in the second half of the cycle. After menopause, the lining typically thins to less than 3 mm. When the lining is thicker than expected, it can signal conditions like polyps, hyperplasia, or in some cases, uterine cancer. For postmenopausal women with bleeding, a lining over 4 to 5 mm usually prompts further testing.
Cervical Length in Pregnancy
During pregnancy, TVS is the standard way to measure the cervix. A cervix that shortens too early can increase the risk of preterm birth. A measurement of 25 mm or less in midpregnancy is considered short in someone carrying a single baby, and a measurement of 20 mm or less before 24 weeks typically leads to treatment with vaginal progesterone to help reduce preterm birth risk.
What to Expect During the Exam
You’ll change into a gown and lie on an exam table with your feet in stirrups or your knees bent. The sonographer or provider covers the probe with a disposable sheath (similar to a condom) and applies lubricating gel. The probe is roughly the width of two fingers. Cleveland Clinic describes the sensation as similar to inserting a larger-than-normal tampon. It shouldn’t be painful, though you may feel mild pressure as the provider angles the probe to get views of different structures.
The provider will move the probe gently to capture images of the uterus from multiple angles, then shift to each ovary. You might feel slight discomfort when the probe presses toward a tender area, but you can always ask them to pause. The whole process wraps up in 15 to 30 minutes depending on what needs to be evaluated.
How to Prepare
Preparation for TVS is the opposite of what you’d do for an abdominal ultrasound. For an abdominal scan, you’re asked to drink at least 24 ounces of clear fluid an hour beforehand and hold your bladder so the full bladder pushes the uterus into a better position. For a transvaginal scan, you should empty your bladder right before the procedure. An empty bladder makes the exam more comfortable and gives the probe a clearer path to the pelvic organs.
No fasting is required. You don’t need to stop any medications. If your provider wants both types of ultrasound (which is common), they’ll typically do the abdominal portion first while your bladder is full, then let you use the restroom before the transvaginal portion.
Safety and Allergies to Mention
TVS uses sound waves, not radiation, so it’s safe during pregnancy and can be repeated as often as needed without any cumulative risk. There are no known harmful effects from diagnostic ultrasound at the frequencies used in clinical practice.
The main safety consideration involves allergies. The disposable sheath covering the probe is often made from latex, and the lubricating gel can contain ingredients like polyethylene glycol (PEG) or chlorhexidine. Allergic reactions during TVS are rare, but cases of anaphylaxis have been reported from both latex exposure and gel ingredients. If you have a known allergy to latex, certain laxative ingredients, or have reacted to medical gels before, let your provider know ahead of time so they can use alternative materials.
TVS vs. Abdominal Ultrasound
These two exams aren’t competing options. They serve different purposes and are often done together. An abdominal ultrasound gives a wider view of the pelvis and is better for surveying large structures like a full-term uterus or very large fibroids. TVS excels at close-up detail: early pregnancies (before 8 to 10 weeks), small ovarian cysts, the uterine lining, and subtle signs of conditions like endometriosis or adenomyosis.
For people who cannot have a transvaginal exam, whether due to anatomy, personal preference, or medical reasons, the abdominal approach is always available as an alternative. The images won’t be as detailed for small structures, but they still provide valuable diagnostic information.