Anomaly Scan: The Exciting Ultrasound With The Scary Name
The Big Scan or the 20 Week Scan: You’re about halfway through your pregnancy, finally feeling pretty good, when suddenly it’s time for the anomaly scan. The name alone sends shivers up the spines of expectant parents everywhere.
What is an anomaly scan?
Despite the scary name, an anomaly scan is a routine and a very important prenatal ultrasound performed around the twentieth week of pregnancy. This scan is a detailed assessment of the development of your baby from head to toe. This scan will also assess the placenta including its placement in the womb. This mid pregnancy scan gives you a chance to come face to screen with the little person growing inside. For some parents, this is the first chance you’ll have to see your baby, and for many more, it is the last time you’ll see baby before you hold him or her in your arms – so exciting!!
Why have an anomaly scan?
Having an anomaly scan is important because it will identify conditions that may benefit from treatment before birth, to plan delivery in an appropriate hospital/centre and/or to optimise treatment after the baby is born. Some women may choose not to be screened at all, or only for some conditions and it is important that we respect that decision.
What happens during an anomaly scan?
During your ultrasound, a Sonographer or midwife will apply a small amount of gel to your belly. The gel allows the transducer (A wand-shaped ultrasound camera) to slide easily over your abdomen and this special wand uses high-frequency sound waves to capture live images of your baby that can be seen on a nearby monitor. Unlike other imaging techniques, ultrasound uses no radiation and for this reason is the preferred method of viewing a developing fetus during pregnancy. This scan takes anywhere from 30 to 45 minutes. That’s a good thing, as it means there is more for you to see as well.
What will I see on the ultrasound?
By 20-weeks, your baby is well developed. Assuming baby cooperates, you’ll be able to see quite a lot! Ultrasound images are black and white and many shades of grey but it is still easy to see the shape of your baby’s nose as well as those tiny fingers and toes. It’s not unusual to see your baby sucking a thumb or yawning and stretching. Gender is also apparent by this time so if you want to keep your baby’s gender a surprise, ask your sonographer to tell you when you should look away from the screen. On, the other hand, if you’d like to know, your baby is developed enough for your sonographer to be able to tell you pink or blue, boy or girl, with accuracy.
An ultrasound demonstrates a lot of real-time moving images of what’s happening inside but many still images will also be taken, to be used for diagnostic purposes. If your baby is in a good position some lovely 3D images can be taken. These keepsake photos can be printed so you can take them home to share with family and friends.
What will the sonographer be looking for?
In addition to measuring your baby’s bones and head circumference (indicators of healthy growth), your sonographer will take a look at several things:
- Head and face: Just like you, your sonographer will be looking at that tiny nose and those rosebud lips. However, the sonographer will also be checking that your baby doesn’t have a cleft lip. There are multiple structures within the head that the sonographer will also check to ensure that the brain is developing as expected.
- Heart: The sonographer will follow the “Tiny Tickers” ultrasound of the fetal heart protocol to make sure the heart has no critical defects. This entails looking at the septum, chambers, great vessels and valves.
- Stomach and abdomen: To make sure your baby is swallowing amniotic fluid the sonographer will look for a stomach bubble which will look like a black spot within the baby’s abdomen. The sonographer will look at where the umbilical cord enters the abdominal wall to make sure there is no defect and that the abdominal wall encases all of the internal organs.
- Kidneys: Your baby’s kidneys have already been hard at work! The sonographer will make sure that both kidneys are present and that urine is flowing freely into the urinary bladder.
- Spine: On an ultrasound, the vertebrae of the spine appear much like a string of pearls. The sonographer will look to see if these “pearls” are aligned and that the baby’s skin completely covers the spine to rule out a neural tube defect.
- Placenta and umbilical cord: The sonographer will check the position of your placenta. If your placenta is low-lying, in other words, if it covers part or all of your cervix (placenta previa), a follow-up scan will be scheduled. If your placenta remains low, it may affect your option for a vaginal birth. The umbilical cord has two arteries and one vein. The sonographer will check the blood flow to the placenta.
- Extremities: The ultrasound will check both arms and legs, hands and feet to make sure all the bones are present.
- Amniotic fluid: The sonographer will measure the amount of amniotic fluid to make sure your baby has plenty of space to move around and that there is not too much or too little fluid.
What conditions can be seen on an anomaly scan?
It’s completely natural to worry that your scan will show something abnormal about your baby’s development. However, we know that most babies are born perfectly normal. (Maybe we should call it the everything’s-fine scan.) If a condition does show up on the ultrasound, knowing about it in advance ensures the right team is on hand to assist when your baby is born.
Here are some conditions that can be seen on an anomaly scan:
- Spina bifida (a spinal cord defect)
- Diaphragmatic hernia
- Missing organs, such as kidneys
- Heart defects
- Cleft lip
- Skeletal problems
- Hydrocephalus (fluid on the brain)
- Missing, or short limbs
- Gastroschisis (Bowel outside the baby’s abdomen)
Does an anomaly scan detect Downs Syndrome?
A 20-week ultrasound is not 100% accurate for demonstrating a chromosomal abnormality and doesn’t always demonstrate all problems. The anomaly scan will, however, check all the usual suspects that may indicate a problem. Some of these are called “soft markers” that appear on an ultrasound. These markers include extra fluid in the kidneys, thickness of the skin on the neck (nuchal), short limbs, and white spots in the heart or abdomen. However, it is really important to know that many normal babies have these markers too.
What if there is a problem?
If your ultrasound detects a problem, the sonographer or midwife will tell you immediately or will contact your doctor so that you can sit and discuss findings in greater detail. You will be given a written report of findings. Your sonographer will answer all your questions as best she can. A scan performed during this time frame will show up most malformations as well as minor ones.
Take a deep breath, this is fun!
Scary names aside, the anomaly scan is one of the most exciting things that will happen during your pregnancy. It’s a chance to get a good look at the little person you’re growing and celebrate being halfway to the finish line. In all likelihood, your scan will show a perfectly healthy baby and you will go home with good news, great memories, and a pocket full of pictures.