Ultrasound at 11-13 weeks of pregnancy

At 11 weeks fetus achieve sufficient sizes so it’s possible to perform detailed examination of its anatomic structures. At this period it’s possible to diagnose evident defects of fetus that incompatible with postnatal life or lead to severe disability. At 11-13 weeks it’s possible to reveal ultrasound markers (sings) of chromosomal diseases of the fetus -  nuchal translucency thickness or  absence of the nasal bone.

The nuchal translucency (NT) is a collection of fluid beneath the fetal skin in the region of the fetal neck. This is present and seen in all fetuses in early pregnancy. The fluid collection is however increased in many fetuses with Down's syndrome and many other chromosomal abnormalities. This is normally less than 2.5mm and when seen increased (greater than 2.5mm, see image on the right) may indicate the baby has Down syndrome or may indicate another chromosomal abnormality. The nuchal translucency normally disappears after 14 week of pregnancy that is why it is so important to have the nuchal translucency measured with an ultrasound between 11 to 14 weeks of pregnancy.

The nasal bone normally becomes visible at the scan since 10 weeks of pregnancy. For a fetus having no visible nasal bone at this period it can also be the sign of chromosomal abnormalities.

To estimate those indications a doctor should have high qualification as getting necessary foreshortening of a fetus at the beginning of the pregnancy demands experience and technical skills. To measure NT a doctor should take the following picture

At the picture only the head and upper-body of the fetus are seen, the profile, nasal bone, NT are distinct.

Quite often such improper pictures can appear: 
examples

improper pictures can

improper pictures can

At those pictures the fetus is crooked, the zooming is insufficient, the profile is indistinct. NT measurements at such pictures are improper and can lead to overestimation or underestimation of the risk for Down syndrome. 

 

The doctors of our centre have the international certificate which gives the right to carry out the scan at 11-13 weeks. The quality of measurements is certified annually. 
To check the doctor’s certificate visit www.fetalmedicine.com

11-13 week scanning is currently the most effective way to identify abnormalities in the early development of a pregnancy such as Down syndrome and others. 
We hope this information to help you to understand why the scan is carried out and why it is so important to have it between 11 and 13 week of pregnancy.