Natural history of trisomy 18.

It has been suggested that survival in babies with trisomy 18 may be better than previously recognised, and that cardiac surgery may be justified. A population based study spanning seven years in one English health region is presented. The fetal prevalence at 18 weeks was 1 in 4274 and birth prevalence 1 in 8333 live births. Trisomy 18 was detected antenatally in 43% of cases, but almost 90% of those born without a diagnosis were known to be growth retarded in utero. More than 50% of liveborn infants were delivered by caesarean section. The median survival of those born alive was 3 days with no babies living longer than one year. Cardiac malformations were not universal but were present in more than 87% of those for whom there were data. However, in only three cases were cardiac problems implicated in the death of the infants. Cardiac surgery is not likely to improve the survival of infants with trisomy 18 and at present cannot be justified. The most common mode of death was central apnoea.