Nuchal translucency is determined by ultrasound examination performed at 11-13.5 weeks of gestational age. This examination offers an opportunity to assess the risks for development of Down syndrome, as well as Edwards and Patau syndroms.
During this examination detailed examination of fetus takes place. Also, confirmation of fetal cardiac activity, examination of fetal head, body and extremities, assessment of placenta, umbilical cord and amniotic fluid are carried out.
With the help of the examination the risks for development of Down syndrome, as well as Edwards and Patau syndromes are assessed. In order to determine the risk of Down syndrome so-called "combined test" is offered for pregnant women, such test includes determination of the above-mentioned nuchal translucency, beta chorionic gonadotropin (HCG) and pregnancy associated plasma protein "PAPP-A". "Combined test" should be performed at 11-13.5 weeks of gestational age. This test gives an opportunity to calculate the risk for Down syndrome with accuracy rate of 95% taking into account a mother"s age.
Conditions for conduction of the examination
• Examination is performed during 11-13.5 weeks of gestational age.
• Examination is generally carried out by transabdominal approach, but in some cases transvaginal approach may be required.
The risk for each woman is calculated on an individual basis taking into consideration the following factors:
• Age of the mother.
• Nuchal translucency.
• Presence or absence of fetal nasal bone.
• Fetal heartrate.
• Assessment of blood flow through tricuspid valve of fetal heart.
• Assessment of blood flow in fetal liver.
• Presence or absence of various physical defects/anomalies.
• Blood levels of two hormones: beta chorionic gonadotropin (HCG) and pregnancy associated plasma protein "PAPP-A".
What additional information is obtained during this examination?
• Determination of fetal viability.
• Establishment of multifetal pregnancy.
• Determination of estimated delivery date.
Possible duration of the examination 20 minutes.
How to prepare for the examination?
Urinary bladder should be filled in order to receive better images during transabdominal examination.
If the examination shows that you are potentially at high risk, the only test confirming chromosomal anomaly are invasive tests: amniocentesis and chorionic villus sampling. In case the examination reveals that you are high risk patient, it is required to have consultations with your obstetrician-gynecologist.
Which is the following examination?
The next ultrasound examination is performed for screening of fetal birth defects at 18 -22 weeks of gestational age.