The detailed anomaly scan (2nd level scan) is the second special ultrasound examination of the fetus, usually performed between 20 and 24 weeks of pregnancy.
As with the 11-13 weeks scan, the anomaly scan evolved over the years to become a thorough check of the fetal anatomy. The fetal organs and systems are examined according to a protocol based on the recommendations of Greek and international scientific societies (www.hellenicultrasound.gr and https://www.isuog.org ). Provided that the examination is performed by a trained and experienced doctor and the protocol is observed, the majority of severe anomalies will be identified.
The anomaly scan aims mainly to identify the major structural defects of the fetus. In addition, one can also look for minor features of Down syndrome (ultrasound markers).
The examination of the blood flow in the uterine arteries provides useful information regarding the chances of complications from the feto-placental unit (pre-eclampsia, fetal growth restriction). This is more important for women that have not had the first trimester assessment for pre-eclampsia.
The measurement of the length of the cervix (the neck of the womb) by transvaginal ultrasound at 20-24 weeks is essential because it leads to the calculation of the risk for very preterm delivery. If a pregnant woman is found to have a very short cervix she is advised to take progesterone, a medication that has been proven to reduce the risk of preterm birth.