This ultrasound scan is one of the most important tests of your pregnancy. It can be done from 19 until 24 weeks (preferably from 20- 22 weeks of pregnancy). It is performed from the tummy, but in case measuring the cervical length or evaluating the exact placenta position needs to be added, the scan is completed vaginally.
What are the purposes of the anomaly scan?
- measuring fetal growth (biometry).
The head, abdomen and long bones (femur, humerus) dimensions will be measured and the estimated fetal weight will be calculated.
- detailed fetal anatomy assessment.
Every fetal system and organ will be sequentially examined. This includes assessment of the fetal head bone density and shape, the brain hemispheres, the ventricles and the cerebellum, the eye lenses, the nose and the nostrils, the palate, the mandible (jaw), the tongue, the lips, the ears, the face profile, the spine curvature, shape and bone density, the neck, the thorax and the lungs, the abdominal wall, the intestines, the kidneys, the bladder, the shape and bone density of the humerus, the ulna and radius, the femur, the tibia and the fibula, the palm, the fingers, the soles and the toes.
- detailed fetal heart anatomy assessment.
Structures assessed inlcude (but are not limited to) the position, the size and the heart angle, the four chambers, the interaventricular and interatrial septum, the major vessels connected to the heart, the aortic arch.
- assessment of the minor (soft) chromosomal abnormalities markers and the re-calculation of the probability of a chromosomal condition.
The soft markers checked are the brain ventricles dimensions, the nasal bone, the nuchal fold, the origin of the right subclavian artery, the intracardiac echogenic focus presence, the renal pelvises dimensions, the intestines echogenicity, the femur length. The presence of one or more of these soft markers does not constitute a problem by itself, it does, however, increase the probability that the fetus has a chromosomal condition. Using dedicated software, we will re- calculate the probability of a chromosomal abnormality as was measured in the 1st trimester.
- determination of the baby’s gender.
If you wish so, we can inform you about the baby’s sex. The accuracy of identifying correctly the gender is 99%.
- placenta localisation and amniotic fluid volume evaluation.
We will confirm the normal amount of amniotic fluid (the fluid around the baby) and also make sure that the placenta is not attached low (very close to the cervix).
- calculate the probability of preterm birth.
If you wish so, you can have a vaginal scan to measure precisely the cervical length in order to inform you about your individual probability of having a preterm birth.
- calculate the probability of preeclampsia and intrauterine growth restriction (IUGR).
This is done by evaluating the blood flow from the uterine arteries (the arteries that supply the womb and the placenta with blood) and you will be informed for the chances these complications of pregnancy may appear.
You have to know that the anomaly scan cannot entirely exclude the probability of a structural abnormality, autism or another genetic syndrome. The detailed anomaly scan has a low sensitivity in identifying chromosomal abnormalities, for example approximately 40% of babies with Down syndrome will appear normal during the scan.However, performing both a detailed scan and using standard views, we can minimise the chances of one of these abnormalities remains undetected.
If any abnormality is detected, the significance of the findings will be comprehensively discussed and the parents will have the chance to get further counseling about the raised concerns.
Additionally, we may discuss about the need of further testing, including the Non- Invasive Prenatal Test ( NIPT or cell- free fetal DNA) or for invasive tests like amniocentesis.