What if the woman for some reason was unaware that she was pregnant until very late,
let's say after seven months of pregnancy?
Then she has to accept that the date she will be given has a potential error of up
to three weeks, even more. The obstetrician will monitor the remainder of the pregnancy
with this factor in mind.
How is the ultrasound scan used to monitor fetal well-being?
If there is any cause for concern on the fetal well-being, the attending obstetrician
may request tests which may be repeated every few days to monitor the fetal condition.
Most tests require the use of ultrasound. This may be to observe the rate of movements,
the tone of the muscles, breathing movements, the amniotic fluid volume and (in some
cases) to check the pattern of blood-flow in the umbilical cord. Most babies do not
require this kind of surveillance.
Safety of ultrasound in pregnancy
How safe is ultrasound?
Karl and Friederich Dussick were the first people to introduce ultrasound as a diagnostic
tool in the medical world. This was way back in 1942 in Austria.
Karl Dussick was in fact a psychiatrist and used this to try to locate brain tumors.
It quickly spread to other branches of medicine and obstetrics turned out to be one
of the most important beneficiaries of this technology. Medical ultrasound has come
a long way since those days.
Vast and extensive studies have been carried out since ultrasound came into widespread
use in obstetrics in the mid-1970s. None has shown adverse effects to mothers or
children involved. We are talking millions of people and a time-scale of decades
into account here.
What is Thermal Index (TI) in ultrasound?
Acoustic (sound) effects produced in normal diagnostic ultrasound in everyday use
is known to be safe whatever the stage of pregnancy. However, depending on the frequency
used and the time duration of the examination, there is potential for the ultrasound
to cause a gradual rise in temperature of the tissues. A temperature rise of up to
1.5°C from a normal baseline (37°C) is perfectly safe. All modern ultrasound machines
display a Thermal Index, an ultrasound safety index which tells the examiner if there
is any rise in temperature and by how much. That way, the examiner ensures that there
is no potentially hazardous rise in the body tissue temperatures. Another safety
index is known as Mechanical Index (MI). It is also displayed continuously. These
measures ensure that the ultrasound examination is always safe for the baby in the
womb and nothing is left to chance.