The B-level examination is a detailed examination of the anatomy of the fetus, which is performed in the second trimester of pregnancy, between 20-24 weeks of gestation.

It is an important ultrasound because it provides us with information about the health, anatomy and the possibility of a chromosomal abnormality before the birth of the fetus, which helps parents to be better informed and make decisions for themselves and their child.

During this ultrasound, every part of the body of the fetus is examined in detail, the position of the placenta, the amount of amniotic fluid and measurements of the growth of the fetus are determined. It also measures the length of the pregnant woman’s cervix and the blood flow in the uterine arteries that supply the uterus and placenta to determine the risk of preeclampsia and premature birth. The examination at MITERA is carried out in accordance with the “Guidelines for ultrasound control in Obstetrics – Ultrasound of the 2nd trimester of pregnancy” of the Hellenic Society of Ultrasound in Obstetrics & Gynecology.

Main purpose of Level B?

The main purpose of the ultrasound is to check the normal course of the pregnancy and to find out if there are rare birth defects or markers of chromosomal abnormalities, which will affect the life of the newborn after birth. If there is a finding in the examination, then the importance of this finding will be discussed with the parents, so that they understand the condition of the fetus, as well as they will be given the option of further examinations of the fetus, so that they will know the possibilities of dealing with the problem .

The percentage of anatomical anomalies that can be diagnosed by ultrasound in the 2nd trimester of pregnancy does not exceed approximately 70% internationally, while for some anatomical systems it may be significantly lower (e.g. for serious cardiac anomalies it does not exceed 50-60% and for minor anomalies or limb anomalies 40%). Absence of anatomical abnormalities in this ultrasound does not imply the birth of a fit and healthy child. Absence of markers of chromosomal abnormalities (findings related to Down syndrome and other chromosomal abnormalities) on this ultrasound does not imply the absence of a chromosomal abnormality, but reduces the possibility of one. Chromosomal abnormalities can only be ruled out by invasive testing (amniocentesis or trophoblast).

What abnormalities are not diagnosed by level B?

There are major abnormalities that go undiagnosed or are diagnosed/worsened after the time period when the 2nd trimester ultrasound is performed. Abnormalities that may occur or worsen after 24 weeks include (but are not limited to) brain maturation disorders, hydrocephalus and cerebral hemorrhages, craniosynostosis, valvular stenosis of the heart and isthmic stenosis of the aorta, hiatal hernia , renal malformations, gastrointestinal obstructions, neurological syndromes and all fetal tumors.

It is also extremely difficult to diagnose cleft palate/lycostoma, midlobe agenesis, closed bifid spine, syndactyly, and in general finger abnormalities, anal atresia, absence of the auditory canal and ear abnormalities, while conditions such as cerebral palsy, mental retardation, deafness, blindness and autism are NOT detected by ultrasound.

The English College of Obstetricians and Gynecologists (Royal College of Obstetricians & Gynecologists-RCOG) recommends that all Hospitals, when performing a b-level ultrasound, inform pregnant women about the possibilities of the examination. Read more here

In conclusion, the β-level ultrasound is the most important and detailed examination of the fetus and is recommended for all pregnant women.