Sex ratio at birth and latitude.
نویسنده
چکیده
منابع مشابه
استفاده از مواد اسپرم کش و غلبه بر حاملگی
The relation between periconceptional vaginal permicide use and sex ratio at birth, birth weight, and the frequency of congenital anomalies was examined in a cohort of 2,712 New York City obstetric patients, 149 of whom (5.5 per cent) became pregnant while using spermicides or had used spermicides before and after conception. Periconceptional spermicide use was not associated with any important...
متن کاملSecular trends in sex ratios at birth in South America over the second half of the 20(th) century.
OBJECTIVES Latitude gradients have been found in the male-female ratio at birth (M/F: male divided by total births), which is anticipated to be 0.515. METHODS Annual national male and female live births by country were obtained for South America from the World Health Organization (WHO) and analysed with contingency tables. The continent was arbitrarily divided into two regions: a region 10° a...
متن کاملHumans at tropical latitudes produce more females.
Skews in the human sex ratio at birth have captivated scientists for over a century. The accepted average human natal sex ratio is slightly male biased, at 106 males per 100 females or 51.5 per cent males. Studies conducted on a localized scale show that sex ratios deviate from this average in response to a staggering number of social, economical and physiological variables. However, these patt...
متن کاملSecular trends in sex ratios at birth in North America and Europe over the second half of the 20th century.
CONTEXT A previous study showed that significantly more boys were born in southern latitudes in Europe than in northern latitudes and the converse pattern was observed in North America. OBJECTIVE This study analyses secular trends in gender ratios for live births over the second half of the 20th century. DESIGN, SETTING, PARTICIPANTS Analysis was carried out from a World Health Organisation...
متن کاملSex Ratio at Birth and Mortality Rates Are Negatively Related in Humans
Evolutionary theory posits that resource availability and parental investment ability could signal offspring sex selection, in order to maximize reproductive returns. Non-human studies have provided evidence for this phenomenon, and maternal condition around the time of conception has been identified as most important factor that influence offspring sex selection. However, studies on humans hav...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
- Journal of epidemiology and community health
دوره 55 3 شماره
صفحات -
تاریخ انتشار 2001