OBJECTIVE To test whether the secondary sex ratio (proportion of male births) is associated with time to pregnancy, a marker of fertility. Design Analysis of four large population surveys. Setting Denmark and the United Kingdom. Participants 49 506 pregnancies. MAIN OUTCOME MEASURE Secondary sex ratio. RESULTS No association was found between the sex ratio and time to pregnancy and no disce...

The significance of migration load in driving the evolution of recipient populations has long been documented in population genetics, but its effects have not been linked to the formation of biased sex ratios in natural populations. In this study, we develop a single-locus model to demonstrate how the migration load can shape the primary and secondary sex ratios in dioecious plants where sexual...

The aim of this study was to evaluate the effect of prenatal exposure to lead, cadmium and mercury levels on the secondary sex ratio. Whole blood samples were collected from pregnant women enrolled in the Avon Longitudinal Study of Parents and Children (ALSPAC) study at a median gestational age of 11 weeks and were analyzed for lead, cadmium and mercury. Regression analysis was used to identify...

Across various animal taxa not only the secondary sex ratio but also the primary sex ratio (at conception) shows significant deviations from the expected equal proportions of sons and daughters. Birds are especially intriguing to study this phenomenon as avian females are the heterogametic sex (ZW); therefore sex determination might be under direct control of the mother. Avian sex ratios vary i...

conclusions the prevalence of ms showed an increasing rate of the disease in recent years. decreasing of the female to male ratio and patients’ low socio-economic level, need more studies. the increasing rate of patients with progressive relapsing feature and more disabled patients belong to this subtype show the poor prognosis. results a total of 142 patients were participated in this study. p...

objective: maternal type and amounts of dietary fatty acids affect on reproductive process in the mice. the present study investigated the effects of maternal supplementation with different amounts of omega-6 or omega-9 during pregnancy on the number of offspring, sex-ratio and duration of gestation. materials and methods: eight-week-old female c57bl/6 mice were randomly assigned into four diet...

some 190 specimens of sefidrud loach, oxynoemacheilus bergianus , were collected from aras river (northwestern iran) and age, size, and some biological characteristics of the samples were investigated from march to july 2013. the maximum age was 3 + years. the specimens ranged in size from 42 to 64mm for males and 45 to 61mm for females in total length, weighing from 0.62 to 2.03g for males and...