USG or Ultrasonography is a very commonly used investigation in pregnancy. The basic mechanism is that sound waves are emitted by the usg probe placed on the abdomen or inside the vagina, which gets reflected back to the probe from the various structures of the baby and around it, to then be converted into an image on the usg machine screen.

1.  WHAT IS USG?
USG or Ultrasonography is a very commonly used investigation in pregnancy. The basic
mechanism is that sound waves are emitted by the usg probe placed on the abdomen or
inside the vagina, which gets reflected back to the probe from the various structures of
the baby and around it, to then be converted into an image on the usg machine screen.
Many patients fear that there are harmful rays in usg that may harm the fetus. But there
are no such rays in usg, I can assure you all of that.
 PURPOSE: usg done at specific times during the pregnancy period to
get information about how the pregnancy is developing, detect the possible
presence of developmental defects both at structural and genetic levels &
predict the development of certain harmful conditions in the developing baby,
so that actions can be taken to prevent those harmful conditions from
developing.
TIMINGS & PURPOSE OF EACH USG:
 6-8 weeks—Known as the ‘DATING SCAN’. It accurately gives the age of the fetus.
Moreover, it detects for the first time the presence of a heartbeat in the baby.
Importantly it also detects the number of developing babies and the exact
location of the pregnancy. (Pregnancy developing in any location other than
inside the uterus is known as ECTOPIC pregnancy & is very dangerous for the
mother, sometimes leading to death if not detected early enough or not treated
properly)
 11-14 weeks—‘NT SCAN’. Simply speaking, the length of a translucent area at
the back of the baby’s neck is measured. Also, the presence of nasal bone is
looked for. Certain blood tests are done with maternal blood. All these data along
with the maternal age at conception is taken into consideration for calculating
the probability of the presence of certain chromosomal disorders and structural
defects in the developing baby. Reported as ‘HIGH RISK’ or ‘LOW RISK’. High-risk
mothers are evaluated more for coming to a definitive diagnosis.
Also, the location of the developing placenta (the organ that is responsible for supplying
all nutrition and oxygen to the baby) is noted in this scan. Location is important as the
placenta develops in the lower part, close to the lower opening of the uterus is a major
concern, as it can result in repeated minor/major bleeding episodes in pregnancy, which
keeps the gynecologist on his/her toes.
 18-20 weeks –
‘ANOMALY SCAN’. As the name suggests we try to find out any anomalies or
abnormalities in the structural growth of the baby. External and internal organs
are checked for anomalies.
 22-24 weeks—

2. ‘CERVICAL LENGTH’ Studies have proved that the length of the cervix (the lower opening
of the uterus from where the baby comes out in a normal delivery), has a good predictive
value for preterm vaginal delivery at around 28-30 weeks. The general consensus is that
the length of the cervix should be more than 2.5 cm at this time & should not be showing
constant decreasing length from earlier scans for assurance about chances of early
delivery being high.
‘FETAL ECHOCARDIOGRAPHY’ is also done during this time to recheck if the heart of the
baby has no anomalies (if it had been missed earlier during the ANOMALY scan).
There is also a way to predict the development of maternal high blood pressure and
slow growth of the baby in late pregnancy, by seeing the speed of flow of blood and its
variations in the arteries of the uterus at this time of the scan.
 28 weeks—
This usg is done to find out if the baby is growing well corresponding to the age
of the pregnancy. Moreover, the amount of fluid around the baby, baby weight,
placental maturity, baby movements, breathing actions, and placenta location
changes in case of the low-lying placenta in earlier scans are some of the other
important things noted.
In my 3 part blog on this topic, I have elaborated on ultrasonographic in various phases
of pregnancy and each of their importance. To know more on this topic you can mail me
at deborjyotipalqueries@outlook.com.
You can also book appointments with me by calling on 9830047058/8017815356 OR you
can go to the appointments section on www.deborjyotipal.com.
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