壓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，在試圖懷孕期間感到有壓力的女性更可能生女孩。
一項研究發現，那些懷孕前數週或數月期間在家庭、工作或感情生活上感到壓力的女性生女孩的機率更高。
牛津大學和美國的研究人員的這一研究發現意味着經濟衰退會讓更多的女性生女孩。此前的研究顯示，在每次大的社會變動之後，出生的男嬰數量都會下降。
例如，在9•11恐怖主義襲擊之後的幾個月，紐約出生的男孩人數急劇下降，而在1991年柏林牆倒塌後的經濟動亂期間，前東德出生的男嬰數量也比預期的少了很多。
不過，這一最新研究首次將日常生活中的壓力和負擔同應激激素水平的上升聯繫了起來。
來自英國各地的338名試圖懷孕的女性每天記錄下自己的生活和性生活，並填寫了有關自己感受到的壓力的問卷。研究人員還測量了她們在懷孕前數月間的應激激素（包括皮質醇）水平。
出生的嬰兒中，58名是男孩，72名是女孩。通常情況下，在英國每出生100個女孩就會出生105個男孩。
如果對這些女性——不論是壓力大的還是淡定的——不加區分，這一結果可能只是概率問題。
不過，研究人員在美國生殖醫學會年會上指出，那些懷孕前皮質醇水平最高的50%的女性顯然生女孩的機率更高。
在佛多裏達州奧蘭多市召開的年會上，研究人員稱，壓力最大的女性生男孩的機率要比壓力最小的女性低75%。人們在承受長時間壓力時，例如工作壓力和戀情不順，皮質醇水平就會上升。
牛津大學的研究人員西西莉亞•派珀博士說，關於錢的煩惱可能也是壓力來源之一。
