Edwards Syndrome (Trisomy 18) by: Karen Guzman

What is Edwards Syndrome? Edwards syndrome (Trisomy 18) is the most common autosomal abnormality among live births after Down syndrome (Trisomy 21). Most trisomy 18 cases result from true trisomy 18, which results from nondisjunction during meiosis. Nondisjunction may occur in the first meiotic stage (MI) or the second meiotic stage (MII). The extra chromosome 18 is of maternal origin in 90-97% of the cases and paternal origin in 3-10% of the cases. Among trisomy 18 cases of maternal origin, 31-39% resulted from nondisjunction in MI and % resulted from nondisjunction in MII.

The live born prevalence is estimated a 1/6,000-1/8,000. The overall prevalence is higher 1/2500-1/2600 due to high frequency of fetal loss and pregnancy termination after prenatal diagnosis. The recurrence risk for a family with a child with full trisomy 18 is about 1%.

Signs of Trisomy 18: 1.Low-Set and malformed ears. 2.Cleft lip and palate. 3.Receding chin. 4.Small head, mouth and jaw. 5.Strawberry-shaped head. 6.Rocker bottom feet. 7.Clenched hands. 8.Central nervous system disorders. 9.Heart defects. 10.Kidney problems.

Risk of Trisomy 18 is well known to increase with increasing maternal age. Race/ethnicity has not been reported to influence risk of Trisomy 18/ One study did find that, of the four racial/ethnic groups (White, Far East Asian, Pacific Islander, Filipino), Trisomy 18 risk was higher for Far East Asians and lowest Pacific Islanders. Geographic area may influence trisomy 18. One study reported higher trisomy 18 rates among urban residents. This increased risk remained after controlling for maternal age. Infant sex influences the risk for Trisomy 18. Females are more likely than males to have aneuploidy. One study found that sex ratio varied with race/ethnicity: however, this observation was attributed to small sample size. Risk Factors:

There is no cure for Edwards Syndrome, however there is testing that can be performed. There is the ultrasound that can detect fetal abnormalities, also a blood test. Survival rates among the infants are not very good. In some cases mothers choose to terminate the pregnancy. The ones that choose to continue with pregnancy about 50% of the babies live longer than 1 week and about 5-10% beyond the first year. The causes of death include but not limited to central apnea, cardiac failure due to heart abnormalities respiratory problems

Mortality Rate Approximately 50% of babies with trisomy 18 live longer than 1 week. 5-10% live beyond the first year. The major causes of death include central apnea, cardiac failure, respiratory insufficiency, aspiration and upper airway obstruction. Infants that survive a year or more tend to experience both mental and physical delays due to abnormalities.

References: National Center for Biotechnology information, U.S. National Library of Medicine ndrome2.shtml 2013 Trisomy 18 Foundation Bharucha B A, Agarwal U M, Savliwala A S, Kolluri R R, Kumta N B. Trisomy 18 : Edward's syndrome (a case report of 3 cases). J Postgrad Med 1983;29:129 Texas Department of State Health Services