Zonta L A, Astolfi P, Ulizzi L
Dipartimento di Genetica e Microbiologia, Università di Pavia, Italy.
Hum Biol. 1996 Jun;68(3):415-26.
We have chosen four Italian regions with different degrees of industrialization and socioeconomic levels to study environmental differences in the sex ratio. The improvement in living and sanitary conditions during the last century has led to a progressive reduction in early male extramortality, and the sex ratio at birth has been almost unchanged at least to the first year of life and probably up to reproductive age. To investigate whether socioeconomic, cultural, or biological factors still influence the sex ratio at birth, we studied the stillbirth rate and the relations between newborn viability and sex composition as a function of maternal age and educational level. Our results suggest that in less favorable environments early selection against male newborns is almost twice that against female newborns when the mothers are the least favored for socioeconomic status, cultural level, and biological conditions (older than 39 years).
我们选取了四个工业化程度和社会经济水平各异的意大利地区，以研究性别比方面的环境差异。上个世纪生活和卫生条件的改善使得早期男性额外死亡率逐步降低，至少在生命的第一年，出生时的性别比几乎没有变化，可能直到生殖年龄都是如此。为了调查社会经济、文化或生物学因素是否仍对出生时的性别比产生影响，我们研究了死产率以及新生儿生存能力与性别构成之间的关系，并将其作为母亲年龄和教育水平的函数。我们的研究结果表明，在不太有利的环境中，当母亲在社会经济地位、文化水平和生物学条件方面最不利（年龄超过39岁）时，针对男性新生儿的早期选择几乎是针对女性新生儿的两倍。
