Trisomy 18:
About 95% of pregnancies that are affected do not result in a live birth. Major causes of death include hypoxia and heart abnormalities. It is impossible to predict an exact prognosis during pregnancy or the neonatal period. Half of the live infants do not survive beyond the first week of life. The median lifespan is five to 15 days... Though rare, some persons with Trisomy 18 do survive into their twenties and thirties.