Dating ultrasound 11 weeks
Accuracy of CRL after 12 weeks in predicting gestational age diminishes and is replaced by measurement of the width of the fetal head (biparietal diameter or BPD).The nuchal translucency (also spelled nucal translucency) is a collection of fluid beneath the fetal skin in the region of the fetal neck and this is present and seen in all fetuses in early pregnancy.During the examination, the fetus is seen by abdominal ultrasound.Occasionally the view is not clear and it may be necessary to perform a vaginal scan.A scan maybe ordered when an abnormality is suspected on clinical grounds.
In the past few years it has been seen that approximately 3 in 4 babies with Down's syndrome do not have a visible nasal bone at the time of the first trimester screening test.
It is this black space that you will see measured during the ultrasound scan.
Currently the most accurate non invasive test for detecting Down syndrome during pregnancy is the measurement of the nuchal translucency with an ultrasound between 11 to 14 weeks of pregnancy.
The fluid collection is however increased in many fetuses with Down's syndrome and many other chromosomal abnormalities.
It is called a 'translucency' because on ultrasound this appears as a black space beneath the fetal skin.
The 12 week scan is a routine ultrasound examination carried out at 10 to 14 weeks of gestation.