Detection Rate of Common Anomalies at the 20 Week Anomaly Scan
Most Anomaly scans are carried out transabdominally (through the tummy) with an abdominal probe and a full bladder is helpful.
The Anomaly Scan will identify about 99% of babies with conditions like spina bifida, about 50% of babies with major heart defects but only a few babies with bone growth problems (skeletal dysplasias). It cannot detect cerebral palsy, autism and learning problems.
The ability to check the baby’s development is dependent upon many factors. The bodyweight of the mother and the manner in which the baby lies in the womb are major issues. However, sometimes we cannot obtain what we consider perfect views of a certain part of the baby’s body. In this case you will be invited back for a repeat scan. This happens in about 10% of cases so please do not be alarmed if this happens to you. You are only charged for the one visit no matter how many times we need to bring you back.
About 70%of all serious congenital malformations can be detected by the 20 week scan. Thus if the baby appears normal on scan there is only a small chance that your baby will have a problem. This is because some problems may not be present at 20 weeks but develop later in the pregnancy e.g. diaphragmatic hernias where there is a small hole in the muscle between the lungs and the bowels.
As well as being scanned by one of our expert sonographers, all our patients will have access to Dr Bryan Beattie, Consultant in Fetal Medicine, for further advice should any problems arise.
We will also give you some black and white photographs of your scan.
We check the development of the following organs or movements on the anatomy scan: head, brain, face, spine, arms, hands, fingers, heart, lungs, bowels, kidneys, bladder, legs, feet, the fluid around the baby, the umbilical cord and position of the placenta.
We have included a table of some of the problems that can be detected on ultrasound at 20 weeks and the likelihood of detection. (in part ref ; RCOG 20)