Relevance of twin data to intrauterine selection: special case of childhood cancer

The purpose of this paper is to draw attention to the statistical implications of abortion risks being greater for twins than singletons, greater for MZ than DZ twins, and greater for one member of a twin pregnancy than both members. This last fact is important, because if one twin aborts the other is usually mistaken for a singleton at birth; thus allowing a given number of nonconcordant abortions to have a marginally greater effect on twin frequency than double the number of concordant abortions.

This feature of abortion hazards is shown in Tab. I, which is based on Sandon's calculations of concordance effects. The figures show how much greater is the effect of a high rate of nonconcordant abortions (Case B) than the effect of an equally high rate of 90% concordant abortions (Case A) or a lower rate of 60% concordant abortions (Case C). In other words, a low frequency of twins in general (and MZ twins in particular) should be typical of an abortion-ridden population and might be a means of recognizing diseases whose prevalence rates are misleading, because they are associated with an abortion hazard (i.e., inherited diseases and diseases acquired during embryogenesis).

Chromosome abnormalities in two cases with bilateral radial element defects

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Ergot poisoning in acute hepatic necrosis

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The chronic patient in the community. A two-year follow up of 338 chronic patients

Three hundred and thirty-eight chronic psychiatric patients were followed up for two years after their discharge. Information was available on all but four patients. During the twenty-four month follow-up period, 11% had died and 25% required readmission. The source of support and living arrangements for the whole group were discussed, and the opinions about the outcome by the informant, psychiatrist, and social worker, were compared, The opinions correlated remarkably well. Characteristics of community care deemed important by the investigators were discussed briefly.