无论你是否意识到，生物钟它都滴滴答答走个不停。每一位处在育龄的女性早上打开电视时，最不想看的新闻一定是：女性在30岁时会失去90%的卵子。
30岁？天啊，生活在三十岁时才刚刚开始呢！
冷酷的事实就是这样，过去几十年的研究证明女性的生育能力随着时间流逝逐渐下降。但是最近研究发现生物钟比我们之前想象的还要早，走的也更快。
一月份的《公共科学图书馆·综合》上刊登了圣安德鲁大学和爱丁堡大学开展的一项研究结果。该研究追踪记录人类的卵巢存量，即女性从受孕到绝经期之间的卵子数量。通过对325名女性的数学模型和数据研究发现，每位女性生来平均带有三十万个卵子，随着年龄增长不断减少，到30岁时剩下12%左右，到40岁时仅剩3%左右。
美国马里兰州罗克维尔市ShadyGrove Fertility中心生殖内分泌学家罗伯特· 斯蒂尔曼说：“这比以前报道的年龄要早，流失的比例也更大。你可能会有争议30岁时到底剩下12%，22%或者是40%的卵子，但可以肯定的是随着女人变老，有效卵子的损失是非常快的。”
渐渐变小的卵巢增加了异常卵子存在的几率。斯蒂尔曼说从女人从35岁往后，每大一岁，生育能力的下降就越明显。
“这些发现进一步证明，对女性来说，关于卵子的一个不幸的事实：要么用了，要么没了。”
其实不用被吓到，三十刚出头时有三万个左右的卵子已经够多了。卵子的数量与质量只是影响生育能力的两个因素。有很多女性在三十多岁甚至四十刚出头也能很好地受孕。再说，治疗不孕不育技术在过去的十年里已经有了很大进步。
《生育与不孕》期刊去年发表的一项研究发现女大学生们大大高估自己在各个年龄段的生育预期。对女性来说，明智的做法是建立一个家庭，或者多要几个孩子，明白年龄增长对受孕以及怀孕的影响。
该研究发起人之一哈米希·华莱士说：“我认为这个研究传递的一个重要信息就是：如果孩子对你来说是非常重要的，那么就不要太晚要孩子。”
女性的生育能力从十几岁开始到二十岁左右达到顶峰，很多美国女性很难接受这样一个生物学现实。根据美国国家健康统计中心，现在很多美国女性每年都在推迟生育计划。2006年，女性平均首次生育年龄是26岁，比1970年的21.4岁推迟了3.6年。
美国生育协会项目负责人克莱尔·维兰：“年轻时我们可能觉得还不成熟，不可以也不应该受孕，但年轻时也恰恰是我们的身体最适合受孕和生孩子的时候。我们寿命在延长，生物钟却未能同步。”
斯蒂尔曼同意这样的说法，同时他指出当前关于晚育年龄和生育健康的研究结果很明显，年龄越老，就越难怀孕，并且出现流产和孕期糖尿病、高血压以及像唐氏综合征这样染色体异常等孕期问题的几率会增加。
一月份的《自闭症研究》发表的一项研究发现孩子得自闭症的风险与母亲的年龄成正比。四十岁以上女性比二十五岁以下女性生下自闭症孩子的几率高出77%。（如果男性年龄超过四十岁，即使女性年龄在二十几岁，风险也会增加。）
斯蒂尔曼说：“社会在变，但是女性卵巢可能需要百万年才能赶上这样的变化。”
我们没有人能等上百万年，所以很多打算要孩子的女性都处于这样一种困境：既要生孩子，又要实现追求更高的教育，成功的事业还有经济稳定等社会目标。
媒体上关于女性生育能力的混乱的报道也让人无所适从。一边是研究结果，充满关于晚育和怀孕方面悲观的数据，一边是时尚杂志，满是四五十岁的名人们，怀抱活泼的孩子，欢喜雀跃，给人感觉女性的生育能力并不像想象的那样有限。
斯蒂尔曼说：“如果你要上人物杂志封面，请坦诚你用了捐赠的卵子，因为别的女人看到杂志会说： ‘我可以等到五十、五十一岁再要孩子啊’。可见，她们误解了。”
尽管如此，以下方面还是值得引起注意的。《公共科学图书馆·综合》关于卵巢存量的研究发现，年龄问题影响女性卵子储备是在25岁之前。美国生育协会的维兰说随着女性逐渐变老，生活压力、吸烟、体重超重等生活方式因素也会对生育能力产生越来越消极的影响。
维兰解释说：“你不能延长生物钟，到一定年龄后你就不能再产生新的卵子，但这并不是影响生育的唯一因素。女性应该提早考虑生育健康问题，并且注意保护身体。”
保持总体健康就是最好的药物。
【原文】
When it comes to fertility, 30 may really be the new 40
BY CAROLYN BUTLER
Washington Post Service
Whether you are aware of your incessantly ticking biological clock or not, the absolute last thing that any woman of steadily advancing childbearing age wants to hear when she flips on the morning news shows is: Women lose 90 percent of their eggs by age 30.
Thirty? Life has hardly begun at 30! Gulp.
The hard truth is that decades of research have proved that a woman’s fertility declines over time. But now it appears that the old biological clock may start ticking much earlier — and faster — than once thought.
A study from the University of St. Andrews and Edinburgh University, published in January by PLoS ONE, tracked the human ovarian reserve — or a woman’s potential number of eggs — from conception through menopause. Using a mathematical model and data from 325 women, the researchers found that the average woman is born with around 300,000 eggs and steadily loses them as she ages, with just 12 percent of those eggs remaining at the age of 30, and only 3 percent left by 40.
“That’s a greater percentage of loss at an earlier age than had previously been reported,” says reproductive endocrinologist Robert Stillman, of Shady Grove Fertility in Rockville, Md. “One might be able to argue whether there are 12 percent remaining at age 30 or 22 percent or even 40 percent, but it is still clear that there’s a very rapid loss in the number of eggs available as women age.”
The smaller pool of older eggs is also more likely to contain a higher proportion of abnormal eggs, he adds, pointing out that from the mid-30s on, the decline in fertility is much steeper with each passing year.
“This adds to the abundant evidence that for women, unfortunately, it’s use ‘em or lose ‘em.”
Before you start freaking out, it’s important to remember that even 30,000 or so eggs remaining at the start of your 30s is still a lot. In addition, quantity and quality of eggs are just two factors affecting fertility. Plenty of women get pregnant perfectly easily in their 30s and even early 40s. Also, infertility technology has come a long way, in even the past decade.
Still, given that a study published last year in the journal Fertility and Sterility found that female undergraduates significantly overestimated their fertility prospects at all ages, it seems wise for women thinking about starting a family — or having more children — to educate themselves about aging’s effects on conception and pregnancy.
“I think the important message is: Don’t leave [having a child] too late, if it is something that is going to be very important to you,” says W. Hamish Wallace, a co-author of the Fertility and Sterility study.
The biological reality that female fertility peaks in the teens and early 20s can be difficult for many American women to swallow, as they delay childbirth further every year, according to the National Center for Health Statistics. Nationally, the average age of first-time mothers in 2006 was 25, up 3.6 years from 21.4 in 1970.
“While we may not be mature enough to conceive at a young age, nor should we, that is still when the body is most adept at conception and carrying a baby,” says Claire Whelan, program director of the American Fertility Association. “Our biological clock has not kept pace with our ability to prolong our life spans.”
Stillman agrees, pointing out that research about advanced maternal age and motherhood today is clear: The older you get, the more difficult it is to get pregnant and the higher the chance of miscarriage, pregnancy problems such as gestational diabetes and hypertension, and chromosomal abnormalities such as Down syndrome, among other concerns.
A study published in January in Autism Research found that the risk of autism increases with a mother’s age: Women over 40 were 77 percent more likely than those under 25 to have a child with the condition. (There was also an elevated risk when the dad was over 40 and the mother was in her 20s.)
“Society has changed,” Stillman says, “but the ovaries will take another million years or two to catch up to that.”
Since we don’t have another million years to wait, many women thinking of having children are left with the predicament of balancing the personal, primal urge to partner up and procreate with worthwhile social goals such as pursuing higher education and a successful career — not to mention economic stability.
It doesn’t make it any easier that the media are filled with mixed messages on women’s fertility: Compare the studies filled with doom-and-gloom statistics on advanced maternal age and pregnancy with the myriad photos of 40- or 50-something celebrities in glossy magazines, gleefully holding their bouncing baby, projecting the image that fertility isn’t as finite as it seems.
“If you’re going to be on the cover of People, you need to be honest and say you’re using donor eggs, because other women look at that and say, `I can wait til I’m 50, 51,’ and they are sadly mistaken,” says Stillman.
There are at least a few things worth noting in the meantime: While the PLoS ONE study on ovarian reserve found that age alone affected a woman’s store of eggs until 25, lifestyle factors such as stress, smoking and being overweight can have an increasingly negative impact on fertility as you get older, say the authors and AFA’s Whelan.
“You can’t prolong your biological clock — you’re not going to produce more eggs — but that’s not the only factor around fertility,” Whelan explains. “Women do need to start thinking proactively about their own reproductive health, and protecting it, as time passes.”
Staying healthy in general may give you a bit of leeway, in other words, but being realistic — and in the know — could be the best medicine of all.
引自：http://www./2010/03/03/v-fullstory/1507993/clocking-out-when-it-comes-to.html
翻译：别大克
