Recurrence Risk of Downs Syndrome

Recurrence risk of Downs Syndrome:--· The cut off is 1 in 150. This means that if ones screening test results show a risk of between 1 in 2 to 1 in 150 that the baby has poissibly Down's syndrome,

· .This is classified as a higher risk result. If the results show a risk of 1 in 151 or more, this is classified as a lower risk result.Recurrence risks for Down syndrome. ... The recurrence risks for Down syndrome due to an inherited translocation are estimated from empirical data in the literature for two maternal age groups: mothers under 30 and mothers 30 and over. These risks were found to be approximately 0.3% and 0.05%, respectively.· Down syndrome is a variable combination of congenital malformations caused by trisomy 21. It is the most commonly recognized genetic cause of mental retardation, with an estimated prevalence of 9.2 cases per 10,000 live births in the United States.1,2 Because of the morbidity associated with Down syndrome, screening and diagnostic testing for this condition are offered as optional components of prenatal care. Prenatal diagnosis of trisomy 21 allows parents the choice of continuing or terminating an affected pregnancy.

· ETIOLOGY AND CLINICAL MANIFESTATIONS

· Down syndrome is usually identified soon after birth by a characteristic pattern of dysmorphic features (Table 1).3,4 The diagnosis is confirmed by karyotype analysis. Trisomy 21 is present in 95 percent of persons with Down syndrome. Mosaicism, a mixture of normal diploid and trisomy 21 cells, occurs in 2 percent. The remaining 3 percent have a Robertsonian translocation in which all or part of an extra chromosome 21 is fused with another chromosome. Most chromosome-21 translocations are sporadic. However, some are inherited from a parent who carries the translocation balanced by a chromosome deletion.

· The cut off is 1 in 150. This means that if ones screening test results show a risk of between 1 in 2 to 1 in 150 that the baby has poissibly Down's syndrome,

· .This is classified as a higher risk result. If the results show a risk of 1 in 151 or more, this is classified as a lower risk result.Recurrence risks for Down syndrome. ... The recurrence risks for Down syndrome due to an inherited translocation are estimated from empirical data in the literature for two maternal age groups: mothers under 30 and mothers 30 and over. These risks were found to be approximately 0.3% and 0.05%, respectively.

J Genet Hum. 1975 Oct;23 SUPPL:1-30.

[Epidemiological aspects of trisomy 21].

Giraud F, Mattei JF.

ABSTRACT

The authors analyse cytogenetic and epidemiological data of 4760 cases of trisomy 21 found .. From the epidemiological aspect, the role of the mother's age was the subject of a special study which confirms the bimodal distribution of the trisomy 21. This distribution is discussed in association with the other epidemiological factors: X-ray, virus, auto-immunity and gynaecological disorders .Another study of nearly 16,000 women, also published in NEJM, confirmed there is high rate of detection and a false-positive rate of 0.06 percent. There are variety of the different types of translocation has been established . That compares with a detection rate of about 79 percent through standard first-trimester screening, and a false-positive rate of 5.4 percent,

Hum Genet. 1980;55(2):203-8.

Recurrence risks for Down syndrome.

Lister TJ, Frota-Pessoa O.

Abstract

The recurrence risks for Down syndrome due to an inherited translocation are estimated from empirical data in the literature for two maternal age groups: mothers under 30 and mothers 30 and over. These risks were found to be approximately 0.3% and 0.05%, respectively. The probability for two Down syndrome sibs both having an inherited translocation was estimated as about 18.2% for the former age group and 2.7% for the latter. The relative effectiveness in preventing. 📷

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