Relationship between urinary estrogen levels before conception and sex ratio at birth in a primate, the gray mouse lemur

BackgroundChina’s sex ratio at birth (SRB) has declined in the past decade but still exceeds the normal level. This study seeks to depict the SRB trend in the past two decades.MethodsWe depicted the SRB trend, including SRB by birth order, children composition, residence and hukou type, education, race and province using latest data available from multiple data sources and standardisation and decomposition methods.ResultsThe SRB remained around 120 in the first decade from 2000 to 2010, and recently declined and approached the normal level during 2010–2020. The SRB for second births and first births converged to the normal level, whereas the SRB for third and above births exceeded the normal level. The rising proportion of second births increased, whereas the decreasing proportion of first births reduced the overall SRB. Parents with only daughters are more likely to abort a female fetus in pursuit of a son, while parents with only sons are more likely to abort a male fetus in pursuit of a daughter. It also shows difference in SRB by residence, hukou type, educational attainment and race. Urban SRB was lower than rural SRB, by the residence and hukou type, but higher than rural SRB after being standardised. Provinces still exhibit differences by original categorised policy even after the implementation of the universal two-child policy.ConclusionsChina’s SRB has declined substantially during the past two decades, but the negative effects need to be tackled.

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Akodon molinae (Rodentia Cricetidae), a new laboratory animal: breeding, management and reproductive performance

Laboratory Animals ◽

10.1258/002367780780942944 ◽

1980 ◽

Vol 14 (2) ◽

pp. 129-131 ◽

Cited By ~ 5

Author(s):

Maria Susana Merani ◽

Marta Susana Lizarralde

Keyword(s):

Sex Ratio ◽

Reproductive Performance ◽

Sexual Maturity ◽

Laboratory Animal ◽

Post Partum ◽

Animal Breeding ◽

Haemorrhagic Fever ◽

Sex Ratio At Birth ◽

Breeding Management ◽

Laboratory Colony

Akodon molinae, a vole mouse widely distributed in central Argentina, shows remarkable chromosome polymorphisms. It is one of the natural reservoirs of the actiologic agent of haemorrhagic fever, and a laboratory colony could be of great help in investigating this disease. Pregnancy lasted 23 (range 21-25) days. Litters of 4-5 young were born to monogamous breeding pairs about every 30 days, with weaning at 26 days post partum. The sex ratio at birth was 505 males to 500 females: at weaning it was 460 to 440. Sexual maturity was attained at about 16 weeks of age in males and 12-20 weeks in females. Akodon molinae is easy to handle, but fighting and killing or neglect of young are problems.

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Effects of assisted reproductive technologies on human sex ratio at birth

Fertility and Sterility ◽

10.1016/j.fertnstert.2014.01.041 ◽

2014 ◽

Vol 101 (5) ◽

pp. 1321-1325 ◽

Cited By ~ 39

Author(s):

Walid E. Maalouf ◽

Mina N. Mincheva ◽

Bruce K. Campbell ◽

Ian C.W. Hardy

Keyword(s):

Sex Ratio ◽

Assisted Reproductive Technologies ◽

Reproductive Technologies ◽

Sex Ratio At Birth

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Human sex ratio at birth and residential proximity to nuclear facilities in France

Reproductive Toxicology ◽

10.1016/j.reprotox.2016.02.008 ◽

2016 ◽

Vol 60 ◽

pp. 104-111 ◽

Cited By ~ 7

Author(s):

Hagen Scherb ◽

Ralf Kusmierz ◽

Kristina Voigt

Keyword(s):

Sex Ratio ◽

Sex Ratio At Birth ◽

Nuclear Facilities ◽

Residential Proximity

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Statistical Study Of The Sex Ratio At Birth

Journal of Hygiene ◽

10.1017/s0022172400043722 ◽

1936 ◽

Vol 36 (3) ◽

pp. 381-401 ◽

Cited By ~ 52

Author(s):

W. T. Russell

Keyword(s):

Sex Ratio ◽

Excess Mortality ◽

Statistical Study ◽

Experimental Studies ◽

Vital Statistics ◽

Conception Rate ◽

Sex Ratio At Birth ◽

Live Births ◽

Natal Mortality

That the number of male births always exceeds that of females is well known to students of vital statistics, but the biological law responsible for the phenomenon has not yet been adequately determined though various theories have been offered in explanation. It has been suggested that it resulted from a high male conception rate which, although modified by an excess mortality of male embryos, nevertheless produced a masculinity of matured births. In more recent times the conclusions drawn by MacDowell & Lord (1925, 1925 a) from their experimental studies with mice have failed to support this view. They claimed that there was no correlation between the pre-natal mortality and the masculinity of live births, that the primary ratio at conception was almost identical with that at birth. These contentions were criticized by Parkes (1923, 1926), who, whilst maintaining the doctrine that the ante-natal mortality of mice “falls preponderatingly upon the males”, stated “that it is quite obvious that a great deal more information is required before any coherent story of the factors governing the sex ratio at birth in the mouse (and all other mammals) can be put together”.

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