- Goldstein H, Nielsen ICG (1988); Rates and Survival in individuals with Trisomy 13 and 18. Clinical Genetics, 34:366-372.
This study looked at survival figures in babies with trisomy 18 and 13 ascertained in a manner that gathered all of the regional patients in a defined 10-year period (1977-1986). The authors examined the survival of 76 liveborn babies with trisomy 18 and 19 babies with trisomy 13. The investigators estimated the prevalence at birth of both conditions,. Survival was similar in both conditions and showed that about 50% of babies died by one week of age and about 90% by 5 months of age.
Comment:
This study represents the third published since the mid-1980's that document survival in an unselected cohort of babies with trisomy 18 during a defined time period. The study by Goldstein is the first population based study of trisomy 13 survival yet published. Previous investigations from the 1960's usually came from smaller series that included the reported series with literature cases. These early studies were limited by selection bias because of literature publications, as well as their inability to demonstrate complete ascertainment (as can occur in the more recently evolved congenital malformation registries). What is of note in all three of these recent investigations is the occurrence of poor survival figures compared to the original papers in the 1960's. In addition to these three literature studies, a Utah investigation published in abstract form, showed similar figures to the three cited papers (Root 5K, Carey JC; 1991 Trisomy 18 survival in Utah, Clin Res 39;64A). All four investigations indicate that about 50% of liveborn infants with trisomy 18 have died by one week of age and about 90% by six months off age. Less than 10% of infants survive the first year of life. All four investigations confirm the previous observation that females survive more than males.
These studies are helpful in the clinical scenario because the figures are applicable to the prenatal diagnostic setting. One important question. however, is why do these recently obtained figures that boast total ascertainment demonstrate poorer survival than the studies of the 1960's? Several factors may account for the differences in these investigations; First, the mean age of diagnosis in one early study was two months of age. This is older than one usually expects to make the diagnosis of Trisomy 18 at the present time. This suggests that many of the infants with trisomy 18 who died in the first week of life were not included in these early investigations. Since trisomy 18 was only recognized in the literature in 1960, and because newborn intensive care nurseries did not start to emerge in general pediatric care until after that time, it is certainly possible that many children went undiagnosed in the 1960's.
Secondly, one could postulate the following; the introduction of prenatal diagnosis, especially by ultrasound, in the last decade has led to more frequent second and third trimester diagnoses of trisomy 18 and 13; this increase in prenatal diagnosis in the latter part of pregnancy allows the doctor and families to have a diagnosis prior to birth and the knowledge of that diagnosis could impact recommendations surrounding delivery management and recuscitation in the newborn period. Thus, one could posit that increased prenatal diagnosis of trisomy 18 has led to change in management strategies. From the Utah study, this author can state that most of the cases were not prenatally diagnosed and thus, were cared for in the obstetric and delivery room setting without knowledge of the diagnosis or its prognosis. Further detailed studies are necessary to sort out whether or not prenatal diagnosis and delivery management options are a factor in survival. This discussion brings up the controversial issue of labor and delivey management in fetuses with trisomy 18 diagnosed in the latter part of pregnancy. Discussion of the literature on this topic is planned for a future newsletter.
Thirdly, we could propose that management of infants with Trisomy 18 is different now than in the 1960's, perhaps due to less aggressive medical care in recent years. This could be the case yet the field of neonatology had hardly developed in the 1960's, 50 to say that infants in the first week of life were treated more aggressively 25-30 years ago does not fit the historical aspects.
One fact does stand out, however; some infants with Trisomy 18 and 13 do survive the first year of life.
- Smith A, Field B, Learoyd BM. Trisomy 18 at Age 21 Years. Am J Med Gen (1989) 36:338-339.
The author of this paper are giving the reader an update on an individual with trisomy 18 that they have reported over the years. This person represents the oldest individual with trisomy 18 in the literature. The authors bring up the point, of course, that survival into adulthood is certainly possible in trisomy 18. |
