1981
DOI: 10.1007/bf01871134
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The changing sex ratio in Japan

Abstract: SummaryThe simultaneous effects of maternal age and birth order on the secondary sex ratio have been examined using data on about 59 million births which occurred in Japan during the period from 1947 to 1978 except 1950. Non-linear negative association between the sex ratio and birth order was observed.The secondary sex ratio in Japan has been increasing during the period of 1900 through 1978. The change in birth order distribution can explain only a part of the increase in the sex ratio. The decrease in still… Show more

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Cited by 15 publications
(9 citation statements)
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“…In the general popula tion, the secondary sex ratio decreased with paternal age or birth order [Imaizumi and Murata, 1981]. In twin births the secondary sex ratio decreased with paternal age except the age group of 25-29 years, but statisti cally not significantly (table II), whereas the sex ratio was significantly lower in primipara than in multipara (table IV).…”
Section: Discussionmentioning
confidence: 81%
See 1 more Smart Citation
“…In the general popula tion, the secondary sex ratio decreased with paternal age or birth order [Imaizumi and Murata, 1981]. In twin births the secondary sex ratio decreased with paternal age except the age group of 25-29 years, but statisti cally not significantly (table II), whereas the sex ratio was significantly lower in primipara than in multipara (table IV).…”
Section: Discussionmentioning
confidence: 81%
“…According to Imaizumi and Murata [1981], the sex ratios among live births and fetal deaths in the Japanese general popula tion were significantly increased with the year during the periods from 1900 to 1978 and from 1948 to 1978, respectively. On the other hand, the sex ratio of twins in live births increased with the year during the pe riod from 1960 to 1967 and in 1974, but the increase was statistically not significant (table I).…”
Section: Discussionmentioning
confidence: 99%
“…Similar results have been obtained by McMillen (1979) analysing the sex-ratio of fetal and neonatal deaths in the United States. Recently, however, Imaizumi and Murata (1981) have reported data from Japan which seem in disagreement with the postponement hypothesis.…”
Section: Introductionmentioning
confidence: 92%
“…For example, excess of male births in relation to epidemic mea sles has been described in African tribes [4]. Hepatitis B virus infection is suspected to be related either to a high male-to-female sex ratio or to a low male-to-female sex ratio in different ethnic groups [3], Thus, the interre lationship between genetic and environmen tal factors might explain both inter-and intrapopulation variations in sex ratio, such as the low male-to-female sex ratio in black births [26] and the increasing male-to-female sex ratio in Japan [27], These observations have some relevance to MS. It is hypothesized that complex inter relationships between viral infections and histocompatibility determinants (HLA class II antigens) play a role in the occurrence of MS [28][29][30].…”
Section: Discussionmentioning
confidence: 99%