The Edward syndrome (also known as trisomy 18) along with Down syndrome (T21) and Patau syndrome(T13), make up the only three trisomies to be compatible with extra-uterine life in non mosaic forms, albeit in the case of Edward's only for a week or so.
After Down syndrome it is the second commonest autosomal trisomy and the overall incidence is estimated to be at ~ 1 : 3000 - 8000. There is an increase in incidence with increasing maternal age.
Trisomy 18 fetuses can have multiple anomalies in multiple systems. Over 130 ! features have been reported. Out of the three main trisomies, this trisomy has highest incidence of major structural anomalies.
- congenital heart disease : 90 - 95%
- central nervous system / spinal abnormalities : 70%
- IUGR : 60 - 90% (tends to occur from early in gestation)
- facial / calvarial abnormalities
- cystic hygroma : ~ 20 %
- skeletal abnormalities
- umbilical cord
- gastrointestinal - thoracic anomalies
- renal anomalies
The following serological markers (often termed a triple screen) are generally lower than expected for that of pregnancy.
- MSAFP : maternal serum alpha feto protein *
- beta human choriotrophic gonadotrophin (bHCG)
The syndrome carries an extremely poor prognosis with a mean infant survival of 48 days 4. The risk of recurrence for a future pregnancy is ~ 1 % greater than that adjusted for maternal age 7.
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