Understanding Obstetrical Ultrasounds

With May being the month we celebrate our mom’s, Mayfair sat down with Helene Hamilton, our lead sonographer, to talk a little bit about what ‘mom’s to be’ can expect during obstetrical ultrasound exams.

Mayfair: In your words, what is an obstetrical ultrasound?

Helene: An obstetrical ultrasound is used to determine the well-being of your baby. It includes seeing your baby’s heart rate and measuring the size of your baby to determine how far along you are.

Mayfair: When would you come in for your first obstetrical ultrasound?

Helene: After confirming with your physician that you are indeed expecting, your physician will fill out a requisition form for you to schedule your first obstetrical ultrasound. We refer to this exam as the ‘Early Obstetrical Ultrasound’ or the ‘Dating Ultrasound’, as it is usually performed in the first trimester of your pregnancy (under 12 weeks). During this exam, we measure what’s called the CRL, which is the length from your baby’s head to rump. Your baby is tiny at this stage. It’s about the size of a peanut, so when we’re measuring, we’re really focused in on our task because it can be challenging to get an accurate measurement.  At this time, we’re also able to determine the number of babies you’re expecting and how far along you are in your pregnancy.

Mayfair: After your Early Obstetrical Ultrasound, what’s next?

Helene: After your first ultrasound, many women will speak with their physician to receive a referral for a Nuchal Translucency Ultrasound to assess the risk of your baby having Down syndrome. This exam is usually performed between 11 and 14 weeks, and requires that we take a measurement of the skin thickness at the back of your baby’s neck.

If you do not have a Nuchal Translucency Ultrasound, your next ultrasound is called a ‘Detailed Ultrasound’. This 40-minute exam is performed at the 18 to 20 week mark of your pregnancy, and involves measuring your baby’s head, abdomen, and the length of your baby’s femur to determine whether your baby is growing at the expected age. We evaluate and image the heart, brain and spine plus your baby’s limbs, abdomen, placenta position and amniotic fluid. If your baby is in a good position, we are also usually able to determine the gender of you baby, but this isn’t a guarantee –sometimes your baby is in the right position, and sometimes not.

Mayfair: Are there other scans required after the 18 to 20 week mark of your pregnancy?

Helene: Yes, referrals for additional ultrasound exams can be scheduled up to 42 weeks. These ultrasounds are typically scheduled to continue to assess the expected growth and wellbeing of your baby. Sometimes babies grow bigger or smaller than expected, so physicians will request another ultrasound to help ensure a healthy pregnancy.

Mayfair: Anything else you’d like to share with mom’s to be about obstetrical ultrasounds? Any tips or tricks?

Helene: Having a baby is such an exciting time for new parents, and we’re so excited for you! On occasion however, it may seem like we aren’t sharing that excitement, this is truly not the case. Measuring your baby during any obstetrical ultrasound is not always easy. We are excited for you, we are just concentrating on retrieving the best possible pictures of your baby for you and your physician.

As far as a tip goes, for your early and detailed obstetrical scans, it’s really important that you come with a full bladder. A full bladder will help us to see your cervix and moves the uterus up so we may be able to see your baby better.