Edwards’ syndrome, also known as trisomy 18, is a genetic disease caused by an extra copy of chromosome 18 in some or in all of the body cells [1,2]. It is the second most common autosomal trisomy after trisomy 21(with an incidence of 1 in 8000 births)  but it is also more serious.
Almost half of trisomy 18 infants die within the first week of life, and the majority of the remaining ones die in the next 12 months because of central apnea, upper airway obstruction, respiratory insufficiency, aspiration, cardiac failure, or a combination of these and other factors [1,4]. Currently most cases of trisomy 18 are prenatally diagnosed, based on screening by maternal age, maternal serum marker screening, or detection of sonographic abnormalities e.g increased nuchal translucency thickness, growth retardation, choroid plexus cyst, overlapping of fingers, and congenital heart defects .Ultrasound scan for fetal anomalies is the most effective screening test for trisomy 18.
A policy of conservative management for women with positive second-trimester biochemical screening or first-trimester combined screening for trisomy 18 is reasonable in the absence of ultrasound fetal abnormalities according to some authors. Unnecessary invasive tests can be avoided . However, when can we decide on a conservative management and when do we need to check by amniocentesis and fetal DNA analyzing? It is a question without a clear answer despite numerous studies and articles on the subject.
In our case the diagnosis was suggested by an ultrasound marker considered minor (choroid plexus cyst) and it would have been missed or found much later if we ignore this marker and we rely on the normal result of first-trimester screening with the nuchal translucency and biochemical markers in normal range.Full text sources