Incidence study of Down's syndrome in Copenhagen, 1960–1971: with chromosome investigation

Abstract

The aim of the study was to obtain incidence figures for Down's syndrome throughout a period where a considerable change in the age distribution of child-bearing mothers has taken place and to study if the expected fall in incidence has occurred. In parts of the Copenhagen Metropolitan area 235 liveborn patients with Down's syndrome were ascertained in the period 1960 to 1971 in a population of 1-2 million with a total of 204771 births. All patients available were examined cytogenetically (75%). In 160 (90-4%) a regular trisomy 21 was observed. In 6-2% of the cases translocations and in 2-3% of the cases mosaics were found. Two double trisomies and a double trisomy mosaic were observed. Throughout the period 1960-71 the percentage of women over 30 years delivering children decreased from 23-4% in the beginning of the period to 16-2% at the end of the period. In the first part of the period 52-6% of the cases were born to mothers over 30, at the end of the period 40% of Down's syndrome mothers were of that age. However, the incidence was unchanged throughout the whole period, about 1-15 per 1000 births. For some age groups a steady rise in incidence of trisomy 21 cases was found throughout the whole period. These findings may be explained by better ascertainment of patients at the end of the period; however, environmental factors may also play a role.

A Cytogenetic Register of Down Syndrome in Lebanon

“…Therefore, the newborn sex ratio in Lebanon does not seem to be higher than that of other white populations. Sex ratios for Down syndrome have varied in different studies, from 0.90 [22]to 1.35 [23]. The sex ratio of Down syndrome in our postnatal series is higher than that, for a sample size of n = 263.…”

Congenital Malformations in Primary Health Care in Al-Qassim Region

“…Some studies with nearly complete ascertainment have found a higher incidence of trisomy-21 in babies born to mothers less than 20 years of age when compared with mothers having an age of 20 to 29 years. 19 As regards paternal age (>25 years), it was also significantly associated with a group of congenital malformations (P<0.05). Though the adverse effects of paternal age on fetal development is fraught with controversies, some experts have highlighted the significant contributions of paternal age 20 and joint effect of parental age 21 to the development of congenital chromosomal syndromes.…”

Gender Affects Clinical Suspicion of Down Syndrome

“…Analysis showed that this increase was accounted for by the growing use of karyotyping to confirm the diagnosis. Among individuals with a clinical diagnosis only, sex ratio was 0.97 (1160 males/1198 females) [Collman & Stoller, 1962;Davidenkova et al, 1965;Huether, 1990;Kovaleva et al, 2001;Staples et al, 1991] while among individuals with confirmed trisomy 21 this figure was 1.31 (1918 males/1466 females) [Huether, 1990;Kovaleva et al, 2001;Mikkelsen et al, 1976;Mikkelsen et al, 1990;Sharav, 1991;Staples et al, 1991;Stoll et al, 1990;Wahrman & Fried, 1970]. Correspondingly, in samples where proportion of clinical diagnosis only was 30% and more, intermediate figure of 1.12 (1950 males/1742 females) [Baird & Sadovnik, 1987;Christoderescu et al, 1977;Johnson et al, 1996;Kallen et al, 1996;Kovaleva et al, 2001;Staples et al, 1991] was observed.…”