In the 24 years since the birth of Louise Brown，the world's first test－tube baby，thousands of would－be parents have been assure that as far as scientists knew there was no extra risk of genetic damage associated with in－vitro fertilization，or IVF．No matter how sperm meets egg--whether in a woman's body or in a Petri dish（and even if the sperm needs some help getting inside the egg）--nature is equally vigilant about preventing serious genetic mishaps from coming to term．With those assurances，test－tube births have soared from a few hundred a year in the early 1980s to tens of thousands today．治疗不孕损害婴儿的遗传基因吗？医生们过去认为不会有什么影响，现在他们对此不十分肯定了。
世界首例试管婴儿路易斯·布朗出生后２４年的时间里，成千上万想做父母亲的人们得到科学家们的保证说，试管内受精对基因不会有什么额外的危险。无论精子如何与卵子结合--是否在女人体内还是在较硬的试管壁上，（即使精子需外力帮助才与卵子结合），大自然都同样会阻止严重变形的基因分娩，有了这样的允诺和保证，试管婴儿的出生在20世纪80年代早期由每年的百余例上升到现如今的数万例。
But according to a pair of reports in last week's New England Journal of Medicine，that conventional wisdom may be wrong．In the first study，doctors in Britain and Australia found that infants conceived with both straightforward test－tube methods and a more invasive technique called intra－cytoplasmic sperm in jection，in which sperm is injected directly into the egg，have an 8.6% risk of major birth defects--including heart and kidney abnormalities，cleft palate and undescended testicles -- compared with the 4.2% rate in babies made the old－fashioned way．The second study，conducted by the U．S．Centers for Disease Control and Prevention（CDC），reported that babies conceived through what doctors call assisted reproductive technologies（ART）have 2.6 times the risk of low or very low birth weight --a significant risk factor for cardiac and cognitive problems．但上周的《新英格兰医学杂志》有两篇报告指出：这种传统的说法也许是错误的。在第一篇研究报告中，英国和澳大利亚的医生们发现，直接的试管受精和通过更具侵入性的技术--把精液通过注射直接与卵子相遇的方法而出生的婴儿，有8.6％存在着主要由出生造成的缺陷的危险性--包括心脏、肾功能不正常、裂腭、男孩隐睾症等。而正常受孕出生的孩子这种现象的比率只为4.2％。第二个研究报告是由"美国疾病控制与预防中心"主持作出的。报告指出，通过医生们所谓"协助生育技术"的方法而受孕出生的婴儿出生时低体重或严重低体重的危险是正常情况的2.6倍。这是引起心脏病和认知能力问题的危险因素。
There are plenty of reasons to take both studies seriously．In the low－birth－weight study，for example，the researchers allowed for the fact that parents who use assisted reproduction tend to be older than average and to have more multiple births--twins，triplets and so on．Even when they corrected for these factors，the disparity between babies conceived through ART and those conceived normally remained．我们有充足的理由对以上两种研究严肃对待。例如：有关低体重出生研究方面，研究者们已然考虑到这样的事实，即那些想通过医学手段而受精生育的夫妻们年龄比一般生育年龄大些，而且一次多胎--双胞胎、三胞胎等等。即使他们避免了这些因素，但是通过"协助生育技术"生育的婴儿与正常生育的婴儿之间仍然存在差异。
But there's no need to panic．Independent experts are quick to point out that the reports are hardly definitive．Couples who seek reproductive help are not just older；they are also--though it may seem like stating the obvious--infertile．"You're comparing two different groups of patients here，"says Dr．William Schoolcraft，director of the Colorado Center for Reproductive Medicine．"You have women with the disease of infertility，and you're comparing them with women who don't have the disease．"Some of the same caveats apply to the birth－defects study，say experts．Here，too，earlier research had found no significant differences between test－tube babies and convention－ally conceived kids．And here，again，the new study didn't correct for the fact that women who get reproductive assistance often have something wrong with their reproductive system in the first place．但也没有必要过分恐慌。其他专家们迅速指出这些报道绝不是确定性的。寻求生育帮助的夫妇并不仅仅是年龄偏大的，他们也是明显的不育夫妇。"科罗拉多生育医学研究中心"负责人威廉姆·斯库克拉夫特博士说："你们是把两类不同的病人进行对比。你们这儿有的是些患有不孕疾病的妇女，而你们却把她们与那些根本没有不孕症的妇女进行对比"。
专家们说，一些同样的防止误解的说明适用于出生缺陷研究。在这里，较早期的研究发现：试管婴儿与正常婴儿没有重大的区别，而且新研究并没有纠正这样的事实，即寻求医学手段而受孕的妇女首先她们本身的生育系统有问题。
Even if these new studies are borne out by later research--already under way in infertility programs in Australia and the U．S．--the risks to kids conceived by assisted reproduction remain reassuringly small．And even if the danger is twice what doctors previously believed，91% of ART babies would still be born perfectly healthy．Says Dr．Zev Rosenwaks，director of New York Presbyterian Hospital's infertility program："If you ask a couple if they would rather not have a child at all or try to have a child that over 90% of the time will be normal，I think they will choose to have the child．"即使这些新研究被后期的研究所证实--在澳大利亚和美国有关不孕项目的研究已经在进行，通过医学受精生育的孩子的出生会有缺陷危险仍然肯定是极小的。即使这种危险是医生们先前相信的两倍，但91％这类出生的婴儿仍然完全健康。纽约基督教长老会医院妇女不孕科主任--兹夫·罗森瓦克斯博士说："如果你问一对夫妇她们愿意一生不要孩子，还是愿意生育一个孩子，而且有多于90％的可能孩子是正常的，我想他们肯定会选择要孩子。" |