"生育危机"真的只是危言耸听吗?

But coordinated studies across Northern Europe found that as many as 1 in 5 young men have sperm counts low enough to affect fertility, according to Richard Sharpe, a male reproductive health specialist at the University of Edinburgh.
但据爱丁堡大学(University of Edinburgh)男性生育健康专家理查德・夏普(Richard Sharpe)说，在北欧展开的联合调查发现，精子数低到影响生育的男性比例已高达五分之一。

The key may be Sertoli cells, which support the testes' germ cells during their 10-week development into becoming sperm. Each Sertoli cell can only support a certain number of germ cells that produce sperm, so the number of Sertoli cells essentially caps a man's maximum production of sperm.
关键之处可能在于支持细胞（Sertoli cell，又译塞托利细胞），这种细胞在睾丸内精子细胞发育成精子的10周过程中为它们提供支持。每一个支持细胞只能支持一定数量的精子细胞，所以支持细胞数量在事实上设定了男性精子产量的上限。

Sertoli cells appear to proliferate in the six months before and after a male child's birth. While outside factors can decrease sperm production, there don't appear to be any that can increase the production above the limit set by the number of Sertoli cells, Dr. Sharpe says.
支持细胞似乎是在男孩出生的前后六个月内增殖。夏普说，外部因素可以降低精子产量，但似乎没有任何外部因素可以将产量提高到支持细胞数量设定的上限之上。

In Dr. Le Moal's study, which she presented last week, she and her colleagues examined data collected by a professional organization in charge of artificial reproductive technique statistics in France, known as Fivnat. The sample consisted of over 26,000 male partners of women who were known to be infertile and going through infertility treatments at clinics around the country from 1989 to 2005. The men weren't known to be infertile, and therefore were considered a more representative sample than studies that focused on men who were seeking treatment for infertility.
莫阿尔在伦敦年会上提交了一份研究报告。在这项研究中，她和同事考察了法国一家名叫“Fivnat”，负责人工生殖技术统计的专业机构收集的数据。样品由2.6万名男性组成；他们的女性伴侣已知不育，并从1989年到2005年在全国各地的医院接受了不孕不育治疗。这些男性是否不育是未知的，因此其代表性被认为优于那些侧重于寻求不孕不育治疗的男性的研究。

The men's semen quality was tested two times in separate laboratories and measured for sperm number, vitality and shape. The researchers averaged the two samples to get a more reliable figure to take into account age and season. In addition, the method of measurement, especially for the sperm's number and vitality didn't change substantially across France during this period, which is a common criticism of such long-term studies, Dr. Le Moal says.
这些男性的精液质量在不同的实验室做了两次检测，测量了精子的数量、活力和形状。研究人员取了两组样本的平均数，以得到一个更可靠的数字，从而把年龄和季节因素考虑进去。莫阿尔还说，这段时期内法国各地的检测方法、特别是测量精子数量和活力的检测方法并没有很大的变化。检测方法的改变是对这类长期研究的常见批评。

They found that during the 17-year study period, men's sperm concentration decreased by nearly a third, or 1.9% a year. In 1989, the average level of sperm for a 35-year-old man was 73.6 million per ml, well above the subfertile threshold, while in 2005 it had dropped to 49.4 million per ml. The results were published in December in the journal Human Reproduction.
他们发现，在这17年的研究期内，男性精子密度下降接近三分之一，即一年下降1.9%。1989年，35岁男性的平均精子密度为每毫升7,360万，远高于弱育的门槛；2005年则已下降到每毫升4,940万。研究结果于2012年12月发表在《人类生殖》(Human Reproduction)杂志上。

Accumulating evidence suggests that early life influences make a difference. Some researchers say that there is a vulnerable period, perhaps between eight and 14 weeks of gestation, in which influences are irreversible. One of the most robust links with decreased sperm count is maternal smoking during pregnancy.
越来越多的证据表明，生命早期的影响会带来不同。一些研究人员说，在生命脆弱期，可能是妊娠八周到14周之间，其受到的影响是不可逆的。与精子数下降相关性最大的因素之一，就是母亲孕期吸烟。

In a study known as Raine of nearly 2,000 males enrolled as babies and now in their early 20s, the size of the testicles was related to total sperm count, and sperm count was more likely to be lower in boys who were born small for gestational age, who were overweight or underweight in childhood or whose mothers smoked during pregnancy.
一项名为“Raine”的研究调查了将近2,000名男性，他们参与调查的时候是婴儿期，现在已经20岁出头。在这项研究中，睾丸的大小与精子总量有关，而在胎龄不足、童年时期过重或过轻、或母亲孕期吸烟的男孩身上，精子数更低的概率更大。

The male's own current marijuana use was also linked to lower sperm count, according to data presented at the conference by Roger Hart, a professor of reproductive medicine at the University of Western Australia.
根据西澳大学(University of Western Australia)生殖医学教授罗杰・哈特(Roger Hart)在年会上提交的数据，男性自己当期吸食大麻也被发现跟精子数更低有关。

Some factors that impact sperm may be reversible. Others have found that how much belly fat men have, even those not overweight, is linked with testosterone levels in young men.
有些影响精子的因素可能是不可逆的。另外一些研究发现，年轻男性腹部脂肪的多少与其睾丸激素水平有关，即便是不超重的男性也是如此。

'By adopting a healthy, balanced diet and lifestyle in pregnancy, you can give your developing baby the very best start in life which will minimize the risk of future diseases,' Edinburgh's Dr. Sharpe says. 'If it's a boy, then this will also make sure that his sperm count, and thus his fertility, is not compromised in any way.' Subscribe to WSJ: http://online.wsj.com?mod=djnwires
爱丁堡大学的夏普说：“通过在孕期采用健康、均衡的饮食和生活方式，你可以给发育中的婴儿最好的人生开端，从而将未来罹患疾病的风险最小化。”他说：“如果生的是男孩，那么这样做还会确保他的精子数，进而保证他的生育能力无论如何都不会遭到削弱。”