Obstetric Dating Ultrasound

Scanning your baby gives you an exciting early glimpse of your baby, but it also provides important medical information relating to your baby’s growth, development and helps determine how your pregnancy is progressing.

Obstetric ultrasounds are performed in the 1st trimester for a variety of reasons, including confirmation of the pregnancy and the number of babies, assessment of bleeding, determining the gestational age and well being.

Your preparation requirements

You will be required to drink 500ml of water one hour prior to your examination. This allows the bladder to fill and helps to visualize the uterus, baby and other structures of the pelvis. Hence, do not go to the toilet once you have commenced drinking the water. If you feel as though you may struggle to hold onto the water, you can come to Sound Radiology prior to your scan to drink the water here.

What to expect

Our ultrasound rooms are dimly lit to reduce the amount of ‘glare’ on our ultrasound monitors. Your partner is welcome to come into the room with you, but as this is a medical diagnostic ultrasound, we do like to limit the number of people who come into the room. If you wish to have more people present, please ask our booking staff when you ring to make your appointment.

You may be asked to change into a patient gown so that we can easily access your abdomen and asked to lie on our ultrasound bed. A warm gel is applied to you which enables us to send the sound waves through the skin to form the image.

While we can usually start seeing the first signs of pregnancy by 5 weeks gestation, a babies heart doesn’t start beating until after 6 weeks gestation. Scans at this early stage are performed to check the viability of your pregnancy, to confirm how far along you are and that the pregnancy isn’t ectopic (outside the uterus). Measurements of the pregnancy sac, the fetal pole (the first signs of baby), your ovaries and kidneys are documented.

When a pregnancy is less than 8 weeks, it is very common to have a transvaginal (internal) ultrasound. This is to accurately measure and assess the pregnancy. If this is required, then your Sonographer will discuss this with you at the time of the scan and you will be asked to empty your bladder. A transvaginal scan does not adversely affect your pregnancy.

If you are having a dating ultrasound, please see our checklist below.