Survival in trisomy 13 and trisomy 18 cases ascertained from population based registers.

Although long term survivors are well documented, infants with the autosomal trisomies 18 (Edwards syndrome) or 13 (Patau syndrome) usually die in the first few days or weeks of life. Accurate estimates of life expectancy are few, particularly in the case of trisomy 13. There have been six population surveys of survival in trisomy 18, comprising 430 unselected cases. In contrast there have been only two such studies of trisomy 13 involving 35 cases. 7 A reliable estimate of survival time is important when counselling parents following a preor postnatal diagnosis. The fact that a significant proportion of infants succumb within the first 24 hours is a major contributing factor to the short median survival time. Given this fact, a means of revising the estimate of survival when an infant is already several days old is important. Using information available on infants with trisomy 13 or 18 born in Scotland from 1974 to 1997, we have calculated median survival times in this population and prepared revised figures which take into account continued survival.