When will I have my first ultrasound?

When you have your first ultrasound depends on how your pregnancy is going, and even where you live.

Early ultrasound
If you've experienced problems, such as a previous miscarriage or bleeding in the first weeks of this pregnancy, your doctor or midwife may recommend an early ultrasound. This takes place when you're between six weeks and 10 weeks pregnant.

Your care provider can usually refer you for an early ultrasound right away, if she thinks it's needed. It is carried out as a vaginal ultrasound rather than through your belly. That's because a vaginal scan can offer a clearer picture of your baby earlier in pregnancy than an abdominal ultrasound. You may also have an abdominal ultrasound.

This early ultrasound should help to reassure you about your pregnancy this time around. If you feel a bit apprehensive about a vaginal ultrasound, you may feel less worried if you:

• Talk the procedure over with your doctor or midwife so you know what to expect.
• Ask a friend or relative to come along to the clinic or hospital with you to provide support.
• Request that a woman carries out your ultrasound.

Dating ultrasound
In most cases, where there are no problems, you'll have two ultrasounds during your pregnancy. The first will be your dating ultrasound which is booked between 10 weeks and 13 weeks plus six days of your pregnancy. During your dating ultrasound, the sonographer will put gel on your belly and move a hand-held device, called a transducer, over your skin. You'll then be able to see a view of your baby.

The ultrasound will:

• Date your pregnancy to find out more accurately when your baby is due. This is calculated by measuring your baby's length from his head to his bottom, called his crown rump length (CRL).
• Reveal if you are carrying one baby, twins or more.
• Check your baby's heartbeat.

A dating ultrasound is a more precise way of establishing your due date than counting from your last monthly period (LMP). An accurate due date is particularly important for the result if you choose to have a screening test for Down syndrome.

First trimester combined screening
At the same time, as your dating ultrasound, you will be offered combined screening, to check for abnormalities. This is made up of:

• A nuchal translucency ultrasound. This can estimate the likelihood of your baby having Down syndrome. The ultrasound is usually done through your belly, though sometimes a vaginal ultrasound offers better views.
• A blood test which detects the levels of the hormone human chorionic gonadotrophin (hCG) and the plasma protein-A (PAPP-A). Abnormal levels of these may indicate Down syndrome.

If you turn out to be less than 11 weeks pregnant when you have your dating ultrasound you will need to rebook for your combined screening.

If you are more than 14 weeks pregnant your doctor or midwife may offer you maternal serum screenings, instead of the combined screenings.
See our overview of ultrasounds to find out more.

Have you seen our images of fetal ultrasound between eight and 12 weeks?

Reviewed for Canada by Suzanne Wong, MD