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Results for “Sex Ratio”

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At least 19 recordsLinked to original sources

PubMed1978

Genetic studies of acute infantile spinal muscular atrophy (SMA type I). An analysis of sex ratios, segregation ratios, and sex influence.

An analysis of segregation and sex ratios, and of sex influence, was undertaken in a series of 78 index patients with acute infantile spinal muscular atrophy (SMA type I). The sex ratio of index patients was 2.0, and the excess of males was shown to occur principally among sporadic cases. The sex ratio of familial cases did not differ significantly from 1.0. The implications of this are discussed. No sex influence on age at onset, or on life expectancy, was present. The segregation ratio (Weinberg Proband method) was 0.29 for all index cases, and 0.26 for all cases excluding those referred specifically to a genetic counselling clinic. Autosomal recessivity is confirmed for this disease, with the probable inclusion of unrecognised male phenocopies in clinical series.

Acute Disease↗

PubMed1978

[Human sex ratio and sex-related selection at birth].

Sex ratio in 11,500 infants died at different perinatal periods (antenatal, intranatal and postnatal) is studied. Sex ratio in these periods is: 107 male : 100 female; 136 male : 100 female; 168 male : 100 female respectively; differences at each period are statistically significant (alpha less than 0.001). A change in differential sex-linked mortality is observed at perinatal period. High mortality in males, which is characteristic of human postnatal ontogenesis, manifests distinctly from the moment of passing on to extrauterine life.

Female↗

PubMed1979

[Seasonal fluctuations in the sex ratio of new borns and the influence of the declining birth rate on the sex ratio (author's transl)].

Seasonal fluctuations in the sex ratio of new borns are investigated. The largest predominance of male deliveries over female deliveries was found to be during the conception months May-June with an almost constant number of deliveries. The highest value was in June. Seasonal maximum of the male to female sex ratio is concomitant to the seasonal maximum of conceptions. The investigation of the yearly sex ratio from 1958-1978 showed changes in the secondary sex ratio concomitant to the increase or decrease of the delivery rate. When the delivery rate decreased below 10 deliveries by 1000 population a reverse in the sex ratio was noted and the lowest number of male deliveries was found. This occurred although the number of first deliveries increased further with the decrease of multiparities. The reasons for this reverse trend in the sex ratio are discussed and a possible relationship to preceeding oral contraception is mentioned.

Birth Rate↗

PubMed1977

Determination of prenatal sex ratio in man.

The sex of a conceptus at the early embryonic state was diagnosed in 1000 induced abortions. Specimens were obtained from women who terminated their pregnancies within 12 menstrual weeks on socio-economic indications. By making use of the triple checking procedures, such as the karyotypic analysis of Giemsa-stained slides, the fluorescent Y chromosome analysis and the Y-body test in interphase nuclei, the sex ratio was determined as 106.6 (516 males/484 females). The sex distribution in the chromosomally normal embryos was 481 in males to 448 in females; that gave the ratio of 107.4. A slight excess of males was already present at his stage of pregnancy. When the ratios were calculated in relation to the maternal age, the lower sex ratio was noted for embryos born to mothers over 30 years. Taking a Y-bearing embryo as male, the ratio in 71 chromosomally aberrant embryos was 97.2 (35 males/36 females). The sex ratio in the cases of chromosome abnormalities was not statistically different from that of thenormal embryos.

Abortion, Legal↗

PubMed1977

Sex selection with biased technologies and its effect on the population sex ratio.

Current biomedical research on sex selection techniques may soon offer couples the opportunity to choose the sex of their children with greater certainty. A technique planned for marketing by mid-1978 can increase the probability of bearing a son to as much as 0.90. However, couples who wish to improve their chances of bearing a daughter have no such opportunity. The purpose of this paper is two-fold. First, a decision-making model is provided which describes how couples should choose among alternative sex-selection methods so as to maximize the probability of bearing their desired number of sons and daughters. Second, the effect of the widespread use of sex-selection techniques on the population sex ratio is explored. It is shown that even if populations have unbiased sex preferences, or sex preferences biased towards daughters, the use of biased sex-selection technologies may result in very high population sex ratios.

Belgium↗

PubMed1979

The sex ratio in spina bifida.

Published reports on the sex ratio of spina bifida have been reviewed. With one exception, there seems to be no evidence of variation in the sex ratio of spina bifida. In particular, unlike anencephaly, the sex ratio of spina bifida seems to be unrelated to the prevalence of the malformation: this (M/(M+F)) is of the order of 0.44 in respect of all spina bifida births (liveborn and stillborn). The sex ratio of spina bifida in Negroes does not seem to differ from that in whites (though the data on this point are not numerous). The exception noted above concerns spina bifida occurrring in twins: these cases are disproportionately often female. The point stands in need of explanation.

Anencephaly↗

PubMed1979

[Sex ratio in hybrid mice CBA X C57BL].

Sex ratio and postimplantation mortality were studied in (CBAXC57BL)F1, CBA and C57BL mouse embryos. It has been shown that female fetuses are predominant in the progeny of hybrid mice. In CBA and C57BL mice the sex distribution was 1 : 1. The disorder in the balanced sex ratio in the progeny of hybrid mice confirms a conclusion on the effect of the mouse genetic features on the sex distribution in embryos. Equal sex ratio in CBA and C57BL mice indicates the absence of selective mortality in the embryos of either sex during embryogenesis.

Animals↗

PubMed1977

[Sex ratio of inbred strains of mice].

A study of the sex ratio in mice of the inbred strains (CBA and C3H) and connection of the postimplantation embryonic mortality in mice of these strains with the sex distribution of embryos demonstrated that the sex ratio in these mice was 1:1. Literature and the author's personal data suggested that genetic features of mice of the inbred strains failed to influence significantly the sex ratio of the offspring. The postimplantation embryonic death rate in the C3H mice exceeded that in the CBA mice (14.4 and 9.3%, respectively). However, the balanced sex ratio in mice of these strains points to the absence of selective mortality of the embryos of any one sex during embryogenesis.

Animals↗

PubMed1979

The question of adaptive sex ratio in outcrossed vertebrates.

Of various published theories of adaptive control of progeny sex ratio only two are plausible, a physiological theory by Trivers & Willard, and a demographic theory by Verner. The first applies to species in which sons and daughters impose different costs on parents, and in which only one or very few young are produced at once. They ought to show positive correlations in the sex of successive offspring and high sex-ratio variance among progenies. Verner's theory postulates a minimization of competition for mates in neighbourhoods subject to random fluctuation in sex ratio. Optimal progenies would exactly match the population's evolutionary equilibrium sex ratio. There would be little variance among progenies. Evidence from vertebrates is unfavourable to either theory and supports, instead, a non-adaptive model, the purely random (Mendelian) determination of sex. The apparent absence of parental control of progeny sex ratio is a serious theoretical difficulty.

Adaptation, Biological↗

PubMed1977

Sex ratio in a sample of human fetuses in Denmark, 1962-1973.

The sex ratio was determined in 791 fetuses from pregnant women in the Copenhagen area 1962-1973. All the mothers were sterilized in connection with an induced abortion. Eighty percent of the fetuses had a crown-rump length between 50 mm and 150 mm corresponding to postmenstrual age of 11-19 weeks. The sex ratio was 138. There was no association between length and sex ratio. The difference between this sex ratio and that for live births in Denmark 1962-1973 (105-9) is substantial.

Abortion, Induced↗

PubMed1975

Maternal ABO groups and the sex ratio of live births.

The sex ratio of 67,205 single, live births was significantly associated with maternal ABO, but not Rh, types. The proportion of males was highest among children of AB mothers in both the Rh+ and Rh- subpopulations, corroborating previous data. The findings are discussed with relation to earlier reports and possible mechanisms.

ABO Blood-Group System↗

PubMed1977

ABO and Rh blood groups in relation to sex ratio, mean number and mortality of sibs.

Data are presented on the sex ratio, mean number and mortality of the sibs of 17,060 schoolchildren, and on the sex ratio and mean number of the sibs of 5,785 blood donors, in relation to the children's and donors' sex and ABO and Rh blood groups. The sex ratio is significantly higher for the sibs of AB + B than for those of A + O schoolboys, and for the sibs of Rh-negative than for those of Rh-positive male blood donors, but in both cases the mean number of sibs is exactly the same for the first-mentioned as for the second-mentioned category.

ABO Blood-Group System↗

PubMed1979

The lack of effect of ejaculate sequence on sex ratio in rabbits.

The influence of the order of the ejaculate on the sex ratio was determined by ejaculating 1 of 5 experimental males 20 times over a period of 2 to 8 h. The sex ratio was noted for the offspring of ejaculates 1, 5, 10, 15 and 20 in a total of 32 litters. The sex ratio of these offspring did not deviate signigicantly from 50:50 (P greater than 0.1) for any ejaculate in the sequence.

Animals↗

PubMedDate not supplied

[Sex ratio and survival rate in embryogenesis and the perinatal period].

Sex ratio was studied among abortuses and infants who died perinatally (9972 cases). Sex begins influencing mortality in the perinatal period, in which a significant increase in the sex ratio is shown (106 males: 100 females--antenatal; 136 males: 100 females--intranatal; 159 males:100 females--within the first 6 days of life).

Abortion, Spontaneous↗

PubMed1976

[Sex ratios in mouse embryos during the postimplantation period of development].

Sex ratio in the embryos if the CBA mice was studied on the 10th and 18th days of gestation to analyze the relationship between the mortality and sex of the embryo. Spontaneous mortality of embryos was shown to be independent of sex of the embryos , and sex ratio of the embryos at different stages of embryogenesis was no different from 1 : 1.

Animals↗

PubMed1979

The secondary sex ratio, paternal age, maternal age and birth order in Japan.

The simultaneous effects of several variables on the secondary sex ratio have been examined using data from over 3.7 million births which occurred in Japan during 1975--6. A weak and negative association between sex ratio and birth order was observed but it was not significant in the statistical sense. A negative effect of paternal age--birth order interaction was obtained when maternal age was controlled. The quadratic model is much more powerful than the linear model in explaining the sex ratio variability.

Adolescent↗

PubMed1979

Fetal sex ratio in the rhesus (Macaca mulatta).

Fetal sex ratio was determined in several hundred timed Macaca mulatta pregnancies terminated by hysterotomy between 75 and 179 days' gestation. From 75 to 149 days' gestation a greater number of females occurred in utero, while after 150 days a greater number of males was observed. However, this difference was not statistically significant.

Animals↗

PubMed1978

The association of sex ratio anomalies with pyloric stenosis.

Published family data were examined for evidence of aberrant sex ratios in relatives of pyloric stenosis index cases. An excess of males over females was found among unaffected members of sibships in which there occurred more than one case of pyloric stenosis. The male excess among affected members of these sibships did not differ from that among index cases without affected sibs. An unusual frequency of spontaneous abortions in these subships, which might account for the observed excess of males, was not observed. No evidence was found of sex ratio anomalies in other classes of relative of pyloric stenosis index cases, whether or not the index cases had affected sibs.

Abortion, Spontaneous↗