Obstetric Ultrasound is the use of ultrasound scans in pregnancy.
Since its introduction in the late 1950’s ultrasonography has
become a very useful diagnostic tool in Obstetrics.
Currently used equipments are known as real-time scanners, with
which a continous picture of the moving fetus can be depicted on
a monitor screen. Very high frequency sound waves of between 3.5
to 7.0 megahertz (i.e. 3.5 to 7 million cycles per second) are generally
used for this purpose.
They are emitted from a transducer which is placed in contact with
the maternal abdomen, and is moved to "look at" (likened
to a light shined from a torch) any particular content of the uterus.
Repetitive arrays of ultrasound beams scan the fetus in thin slices
and are reflected back onto the same transducer.
The information obtained from different reflections are recomposed
back into a picture on the monitor screen (a sonogram, or ultrasonogram).
Movements such as fetal heart beat and malformations in the feus
can be assessed and measurements can be made accurately on the images
displayed on the screen. Such measurements form the cornerstone
in the assessment of gestational age, size and growth in the fetus.
A full bladder is often required for the procedure when abdominal
scanning is done in early pregnency. There may be some discomfort
from pressure on the full bladder. The conducting gel is non-staining
but may feel slightly cold and wet. There is no sensation at all
from the ultrasound waves.
Why and when is Ultrasound used in Pregnancy?
Ultrasound scan is currently considered to be a safe, non-invasive,
accurate and cost-effective investigation in the fetus. It has progressively
become an indispensible obstetric tool and plays an important role
in the care of every pregnant woman.