At 19-20 Weeks: Morphology Scan
At 12 weeks, you should have had your nuchal translucency (NT) scan to determine your due date, the number of babies present and the risk of Down syndrome or other chromosomal abnormalities. At 19-20 weeks, nearly all pregnancies in Australia undergo a morphology scan referred to as a “genetic scan” or “anomaly scan”.
This scan is used to assess:
- fetal structural development including brain, face, spine, heart, Lungs, stomach, kidneys, bladder, arms and legs
- fetal growth
- placental position and cord insertion
- amniotic fluid volume
- cervical length
You will notice a dramatic difference between your 12-week scan and this scan.
3D / 4D Images at 18 weeks
3D / 4D Images at 19 weeks
An amazing amount of detail can often be seen in the morphology scan. However, it is important to realize that not all parts of the baby show up well with ultrasound. No ultrasound examination can ever guarantee a normal fetus. The best centres in the world consistently report on the limitations of ultrasound and its inability to detect all fetal abnormalities. Up to half of fetal heart defects will not be seen. Some of these are only minor, but some may not be apparent until the fetus is bigger, later in the pregnancy. Many bone growth problems, including forms of dwarfism, will only be possibly detectable late in pregnancy and the diagnosis is made from x-rays taken after the baby is born. Conditions such as cerebral palsy, blindness, deafness, autism and most skin and soft tissue lesions are never detected with ultrasound. The fetal position and size of the maternal abdomen are important factors that affect fetal anomaly detection. It is better if your bladder is not emptied just before the scan as it helps push the uterus above your pubic bone and generally makes the scanning more technically satisfactory. We don’t require you to be uncomfortable. Water, tea and coffee are available in our waiting room.
Diagnosing Down syndrome
Down syndrome is a problem whereby every cell in the body has an extra chromosome 21. There is no specific diagnostic finding on ultrasound. It is necessary to look at fetal cells through a microscope to diagnose a chromosomal abnormality. Therefore, chromosomal lesions such as Down syndrome cannot be diagnosed with ultrasound. Some 40% of Down syndrome fetuses will appear normal on the 19-20 week scan. Sometimes, there may be some ultrasound findings that can make us suspicious of an increased chance that the fetus has a chromosome lesion. However, non-invasive ultrasound screening for chromosome lesions is best done at the 12-week NT scan.
Determining the sex of your baby
The sex of your baby can often be determined on this scan. Ultrasound is never 100% accurate and fetal position and cooperation will play a big part. If you don’t wish to know the sex of your baby, please tell us at the start of the examination so we can tell you when to look away from the screen.
Safety and comfort
Ultrasound has been used throughout developed countries all over the world for the past 30- 40 years and no significant harmful effects of obstetric ultrasound have been shown. It is considered safe. For your comfort, you are welcome to bring your partner or support person. Children under the age of 6 are not permitted in the scan rooms.