The target or anomaly scan (18 – 20 week) is the single most important scan during a pregnancy. Its like a head to toe clinical examination of the fetus. During this scan, the head, face, heart, lungs, stomach, bladder, kidneys and limbs of the fetus are thoroughly scanned. Fetal activity is also observed during scanning. The umbilical cord, location of the placenta, which gives nutrition to the baby and the amniotic fluid that surrounds the fetus are examined. The length of the cervix of the uterus is measured.

In some instances, a "Doppler Study" is performed to evaluate the blood flow to various parts of the baby especially the placenta and the brain. Blood flow to other organs may be studied in the indicated cases.

It is important to remember that majority of babies are normal. Birth defects are seen only in 1 – 2% of pregnancies. In some cases, there may be some minor variations observed during the scan. This should not cause anxiety and the expert can help to understand these findings better.

A detailed ultrasound examination of the baby is essentially done to ensure and give the reassurance that the baby is normal. In about 2 % of the general population and in some women with medical problems or a family history of genetic diseases there is a possibility of an abnormality in the baby. An ultrasound exam done by a person who is experienced in obstetric ultrasound can pick up a large number of such anomalies.

Ultrasound at 20 weeks of gestation is done following the guideline "Rule of 3" adopted from Mediscan, Chennai.