Trisomy 18

Known as Edwards syndrome.

Occurs in approximately 1 of 3000 live-born infants, although the numbers are higher when early pregnancy losses are factored in that occur in the 2nd and 3rd trimesters.

Intensive care admissions in Neonatal units are most common for infants with Trisomy 18.

Baby boys will experience higher mortality rates in this neonatal period than baby girls.

Those with higher birth weights do better across all categories.

Less than 10 percent survive to their first year.

Only 50% liveborn births live to 2 months.

Patients have a tendency to be born preterm or post term (Jones JK).

Some children may live many years.

A small number of adults (usually girls) live into their twenties and thirties.

The second most common trisomy.

The most common type of trisomy 18, occurring in about 95% of all cases, is full trisomy.

With full trisomy, the extra chromosome occurs in every cell in the body.

Full trisomy is not inherited.

Partial trisomy 18 occurs when only part of an extra chromosome is present, and is very rare.

Some partial trisomy 18 syndromes may be caused by hereditary factors.

Mosaic trisomy is very rare and occurs when the extra chromosome is present in some of the cells of the body.

Mosaic trisomy is not inherited and is a random occurrence that takes place during cell division.

Clinical manifestations of the process include: Heart defects such as ventricular septal defect,atrial septic defect, and aortic coarctation kidney disease, omphalocele, esophageal atresia, polyhydramnios, clenched hands, choroid plexus cysts, rocker bottom feet, delayed growth, micrognathia, microcephaly, low-set ears, abnormal head shape, developmental delay, umbilical and inguinal hernias.

Associated with decrease in second trimester maternal serum alpha-fetoprotein and unconjugated estriol and decreased human chorionic gonadrotropin levels.

Major causes of death include apnea and heart problems.

Cannot predict prognosis during pregnancy or neonatal period.

Median survival 5-15 days.

One percent live to age 10 years.

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