压力大的女性更容易生女孩

Women who are stressed while trying for a baby are more likely to have girls, research suggests.

A study found that those who were under pressure at home, work or in their love life in the weeks or months before becoming pregnant had higher than usual odds of giving birth to a daughter rather than a son.

The finding, by Oxford University and US researchers, means the economic downturn could see more women give birth to daughters. The study follows others that have shown the number of baby boys goes down following major upheavals.

For instance, in the months after the 9/11 terrorist attacks, the number of boys born in New York plunged, while the economic chaos that followed the collapse of the Berlin Wall saw far fewer boys born than expected in the former East Germany in 1991.

But the latest study is the first to link the phenomenon to the stresses and strains of everyday life and to rising levels of stress hormones.

Some 338 women from around the UK who were trying to get pregnant kept diaries about their lives and sex lives and filled in questionnaires about how stressed they felt. Levels of stress hormones including cortisol were measured in the months before pregnancy.

Of the babies born, 58 were boys and 72 were girls. Normally, in Britain 105 boys are born for every 100 girls.

When all the women were put together – stressed and calm – the result could have been due to chance.

But among the 50 percent of the women who had the highest amounts of cortisol before pregnancy, the sex ratio was clearly skewed towards girls, the American Society for Reproductive Medicine’s annual conference heard.

The most stressed women were up to 75 percent less likely to have boys than the least stressed, the conference in Orlando, Florida, was told. Cortisol levels rise when people suffer long-term stress such as pressure at work and bad relationships.

Money worries may also play a part, said Oxford University researcher Dr Cecilia Pyper.

研究表明，在试图怀孕期间感到有压力的女性更可能生女孩。

一项研究发现，那些怀孕前数周或数月期间在家庭、工作或感情生活上感到压力的女性生女孩的几率更高。

牛津大学和美国的研究人员的这一研究发现意味着经济衰退会让更多的女性生女孩。此前的研究显示，在每次大的社会变动之后，出生的男婴数量都会下降。

例如，在9•11恐怖主义袭击之后的几个月，纽约出生的男孩人数急剧下降，而在1991年柏林墙倒塌后的经济动乱期间，前东德出生的男婴数量也比预期的少了很多。

不过，这一最新研究首次将日常生活中的压力和负担同应激激素水平的上升联系了起来。

来自英国各地的338名试图怀孕的女性每天记录下自己的生活和性生活，并填写了有关自己感受到的压力的问卷。研究人员还测量了她们在怀孕前数月间的应激激素（包括皮质醇）水平。

出生的婴儿中，58名是男孩，72名是女孩。通常情况下，在英国每出生100个女孩就会出生105个男孩。

如果对这些女性——不论是压力大的还是淡定的——不加区分，这一结果可能只是概率问题。

不过，研究人员在美国生殖医学会年会上指出，那些怀孕前皮质醇水平最高的50%的女性显然生女孩的几率更高。

在佛多里达州奥兰多市召开的年会上，研究人员称，压力最大的女性生男孩的几率要比压力最小的女性低75%。人们在承受长时间压力时，例如工作压力和恋情不顺，皮质醇水平就会上升。

牛津大学的研究人员西西莉亚•派珀博士说，关于钱的烦恼可能也是压力来源之一。