This scan is best done at 18 – 20 weeks. This scan is done to study all the fetal parts in detail. All the fetal structures have been formed by this time and develop as the pregnancy advances. In this ultrasound examination is done to assess the fetal growth and to rule out any structural malformations.
This scan is done for:

• Assessment of fetal growth
• To study the fetal structures in detail: During the scan we examine each part of the fetal body in detail. Special attention is paid to the brain, face, spine, heart, stomach, bowel, kidneys and limbs. If any abnormalities are detected the significance of the findings is discussed and the parents are counselled accordingly.
• Genetic Sonogram: For risk reassessment of chromosomal abnormalities
• Determine the position of placenta
• Assessment of amount of amniotic fluid
• Measurement of cervical length

Certain abnormalities in the fetus may be associated with chromosomal and genetic abnormalities and have a bearing on the future pregnancies. In case of detection of any structural abnormality in the fetus, further steps can be taken to try and identify the cause and provide counselling about the same.

Who should have a Fetal Anomaly Scan?

The vast majority of babies are born normal. However all women, irrespective of their age, have a minimal chance of having a baby with structural abnormalities which may cause physical or mental limitation. Many such abnormalities can be diagnosed and ruled out with the fetal anomaly scan. Therefore, it is recommended that all pregnant women should have a fetal anomaly scan.

Is ultrasound examination safe in the pregnancy?

Ultrasound examinations have been used for 40 years to monitor pregnancies. So far the evidence has been reassuring that ultrasound examination is absolutely safe for the mother and the fetus.

What is the duration of this examination?

Most examinations will take between 30 and 40 minutes but these scans depend on the baby’s position and occasionally you will be asked to wait longer to allow your baby to move into a more favourable position.

What might be seen?

The doctor will show to you your baby’s heartbeat and parts of the body like the face and hands, before looking at it in detail.

It might be hard for you to make out your baby’s organs, because the doctor will look at them from various angles and sections.

The baby’s bones appear white on the scan and the soft tissues looks grey and speckled. The amniotic fluid surrounding your baby appears black.

Most of the serious abnormalities can be detected on an ultrasound scan. However, it is not possible to see all abnormalities and some will be detected only after birth. Some conditions such as cerebral palsy and autism can never be seen on a scan.

The quality of the scan image depends on many factors, including the position of the baby and the size of the mother. For example, it will be more difficult to see the baby clearly if the mother is overweight. A poor image will affect our ability to see problems.

Can Down syndrome or chromosomal abnormalities be seen on the scan?

This scan can also identify 50% to 60% of cases of Down syndrome, but the First Trimester Screening (FTS) test is definitely better for this. Because 30% to 50% of cases of Down syndrome appear normal on ultrasound, only an amniocentesis (testing the fluid surrounding the baby for its chromosomes) can give you this information for certain.

Sometimes babies with chromosomal abnormalities have signs called ultrasound markers. These include in order of importance thick skin behind the neck (nuchal fold), absent nasal bone, mild fluid within the ventricles of the brain, aberrant subclavian artery in the neck, occasionally short arms or legs, white spots in the baby’s heart or abdomen, or choroid plexus cysts in the brain.

While some babies with chromosomal abnormalities have these markers, it is important to remember that many normal babies also have these signs. The only way to diagnose or exclude a chromosomal problem for certain is to have an amniocentesis.

Is full bladder required for the fetal ultrasounds?

The patient needs to hold urine only for the fetal vibility scan i.e the first scan done at 6-8 weeks. Full bladder is not required for any other fetal ultrasound examination

Is the mother required to come empty stomach for fetal scans?

The mother should always eat and come to the hospital. No fetal examinations require the mother to be an empty stomach.