Vaginal ultrasound in pregnancy

A vaginal ultrasound is an ultrasound scan taken using a transducer (probe) that is inserted into your vagina. Vaginal ultrasounds are also called 'internal ultrasounds' or 'transvaginal ultrasounds'.

A vaginal ultrasound may be recommended in early pregnancy or mid-pregnancy.

Early pregnancy

During early pregnancy, a vaginal ultrasound can be done to:

• confirm you are pregnant — it can detect the baby's heartbeat very early in your pregnancy
• help work out your due date
• show if you are pregnant with one baby or more (such as twins or triplets)

Mid-pregnancy

A vaginal ultrasound may be recommended midway through your pregnancy to measure the length of your cervix. That's because having a shorter cervix is associated with an increased chance of premature birth.

If you are found to have an increased chance of premature birth, your doctor may recommend treatment to reduce your risk of early labour.

Sometimes, a vaginal ultrasound may be recommended during early pregnancy to:

• detect an ectopic pregnancy (when a fertilised egg implants outside the womb, usually in one of your fallopian tubes)
• work out the reason for vaginal bleeding
• diagnose a miscarriage

A vaginal ultrasound can be done in a hospital, clinic or consulting room.

Your comfort, dignity and privacy should be protected before, during and after the test. You have the right to stop the test at any point if you feel uncomfortable or want to stop.

Before the test

The test should be explained to you beforehand. You should ask questions and will be asked to give your consent before the test is started. You may be asked to sign a written consent form.

If you are not comfortable having a male perform the test, you can ask for a female sonographer. You can also ask for a female health worker to accompany you for support. Or you can have a friend or family member with you.

You'll be asked to empty your bladder (wee) before having a vaginal ultrasound.

You'll be asked to take off your clothes from the waist down. You may be given a special gown to wear. The doctor or sonographer should give you privacy to change and provide a sheet to place over your lower body.

You will be asked to lie on an examination table with your knees bent. There might be stirrups, or your hips might be slightly raised.

During the test

The test involves having a transducer (probe) gently inserted into your vagina. The transducer is a special smooth, hand-held device. It's slightly larger than a tampon. It will be covered by a sheath and warm lubricating gel.

You should be given the choice of inserting the transducer yourself, which is like inserting a tampon. Otherwise, it can be inserted by the person doing the test. This may be a doctor or specialist sonographer.

The probe will be moved slightly to get clear images. It usually doesn't hurt, but you will feel pressure and it can be uncomfortable. The test usually takes about 15 to 30 minutes.

You can ask to stop the test at any time if you feel uncomfortable.

The main benefit of vaginal ultrasounds is that they can give very clear and detailed images. The images are often more detailed than ultrasounds where the probe is used only on your tummy.

Compared with an abdominal ultrasound, a vaginal ultrasound can allow for:

• a more accurate diagnosis
• earlier detection of pregnancy

Vaginal ultrasounds are generally safe for you and your baby.

Vaginal ultrasounds should not be done if:

• your waters have broken
• you have bleeding associated with placenta praevia ('low-lying placenta')
• you do not want to have the test

If you are allergic to latex, let the sonographer know so they can use a latex-free sheath on the probe.

Often, you can see the ultrasound images on a monitor while you have your scan. If your specialist is there, they might discuss the results with you straight away.

If your specialist isn't there, the sonographer is usually not allowed to discuss what they see with you. Your doctor or midwife will see the images after they have been processed. It usually takes a day or 2 to get the results.

You may feel uncomfortable about having a vaginal ultrasound. Many women find internal examinations stressful or embarrassing. Your personal history or cultural values and beliefs may make this test distressing.

Talk with your doctor or midwife about how important the test is in your situation and about alternative tests. You can always refuse this test.

Having an ultrasound where the transducer is put on your tummy to take images may be offered instead. But the results may not be as accurate.

Talk to your doctor or midwife if you have questions or concerns about having a vaginal ultrasound.

Inside Radiology has information on vaginal ultrasounds.