The nuchal scan is an examination that can be carried out transabdominally or transvaginally. The aim of the nuchal scan is:
To date the pregnancy accurately
This is of great importance, especially for women who do not remember the first day of their last period (LMP) or have conceived during breastfeeding. By measuring the crown-rump length (CRL) we can calculate the estimated due date (EDD).
Diagnosis of major fetal abnormalities
Major fetal abnormalities i.e. of the heart (hypoplastic left heart, bladder (megacystis) and brain and skull (acrania), can be detected in this stage of pregnancy. However, since the fetal organs are constantly developing, it is necessary to conduct the 20 week anatomy scan to check in detail the anatomy of the fetus.
Assess the risk for Down’s syndrome or other chromosomal abnormalities
Nuchal translucency is the sonographic appearance of the liquid behind the fetal neck during the nuchal scan. The thickness of nuchal translucency increases normally according to the age of the fetus. The larger the measurement appears in the scan, the bigger the possibility of the fetus to have a chromosomal abnormality. We estimate the possibility of the fetus having Down’s syndrome individually for every woman by taking into consideration the following factors:
- The woman’s age
- History of previous pregnancy
- Measurement of PAPP-A and β-hCG hormones in maternal blood
- Findings of ultrasound examination
- The nuchal translucency
- The nasal bone
- Blood flow through the fetal heart and ductus venosus
Through the examination of the factors mentioned above, we can diagnose 9 out of 10 fetuses that have Down’s syndrome (95% sensitivity for percentage of false positive results almost 3%).
The result of nuchal scan will be a number that represents the possibility of the specific fetus to have Down’s syndrome. If for example, the possibility is 1:1000 it means that if we had 1000 women one would have a fetus with Down’s syndrome and the remaining 999 would have normal babies. This method of measuring the possibility for Down’s syndrome is very accurate and its results have been confirmed in thousand women worldwide. However, it is not diagnostic meaning that it cannot 100% reassure you that the fetus does not have Down’s syndrome.
The doctor is a Fetal Medicine specialist certified by the Fetal Medicine Foundation in London (FMF), which has developed the method of nuchal translucency test. FMF is in charge of auditing the results from all certified medical practitioners worldwide, so that it maintains a high level of standards.
Assess the risk of preterm birth
Almost 50% of the cases concerning preterm birth before 34 weeks of pregnancy are tightly connected with short cervix. The cervix is the lowest part of a woman’s uterus that is dilated during the childbirth. An examination of the cervix with transvaginal ultrasound scan is an important tool for detecting pregnancies at increased risk of preterm birth.
Assess the risk for developing pre-eclampsia
The main cause of pre-eclampsia is the poor development of the placenta. We can predict this severe obstetric complication by assessing the blood flow in the woman’s uterine arteries with Doppler method, her blood pressure and the results of specific blood tests. If the risk of pre-eclampsia is increased, it is suggested that aspirin is given to the pregnant woman according to the doctor’s guidance, and on condition that there are not contraindications.