Abstract
Between 1968 and 1970, 3441 preschool children were included in a national study of nutritional status based on a probability sample drawn by the Univ. of Michigan Survey Research Center. The purpose of this report is to comment on the geographic distribution of 29 like-sex twin pairs, 17 of which were female-female. From radiographs (metacarpal-phalangeal profile patterns), anthropometry, biochemical determinations and correspondence with families, it appeared that nearly half the like-sex twins were identical. Altogether, 90% of like-sex twin pairs (26) lived in the northern half of the country (above latitude 37.5°) although only 55% of the study population lived in the northern half of the country. Further analysis of data suggested some relation between frequency of like-sex twinning and altitude. Only 7.5% of the study population resided at elevations greater than 900 meters above sea level but it accounted for 40% (12 pairs) of like-sex twins. Four pairs of like-sex twins (3 F-F and 1 M-M) were encountered in one California county at an elevation of 2000 meters.
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Owen, G. GEOGRAPHIC DISTRIBUTION OF LIKE-SEX TWINS IN THE U.S.. Pediatr Res 8, 345 (1974). https://doi.org/10.1203/00006450-197404000-00030
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DOI: https://doi.org/10.1203/00006450-197404000-00030